What is in topsoil is a fair question to ask before you spread a few tons of it across your yard, and the answer is more interesting than “dirt.” Topsoil is the top few inches of the ground, the dark, living layer where roots grow and where almost all of a garden’s activity happens, and it is really a blend of four ingredients in roughly steady proportions. About 45 percent of healthy topsoil by volume is mineral particles, the ground-up rock we call sand, silt, and clay. Another 5 percent or so is organic matter, the decayed remains of plants and animals that give good soil its dark color and much of its fertility. The remaining half is not solid at all: roughly 25 percent is water and 25 percent is air, both sitting in the spaces between the solid particles. On top of that mix live billions of microbes, along with earthworms, fungi, insects, and the fine roots of whatever is growing above. This guide breaks down each of those parts, explains what screened topsoil is and how it is sieved, answers the common questions about whether topsoil contains rocks, clay, sand, and nutrients, covers how well it drains, and takes an honest look at what is actually in a bag of topsoil, which varies more than most people expect.
Once you understand what topsoil is made of, work out how much you need by plugging your bed size and depth into the Dirt Calculator or the Topsoil Calculator, so the right blend of minerals and organic matter arrives in the right amount.
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What is topsoil made of? The four-part mix
Ask a soil scientist what is in topsoil and you will get a surprisingly tidy answer, because healthy topsoil follows a fairly consistent recipe by volume. Roughly 45 percent is mineral matter, meaning weathered rock broken down into particles of sand, silt, and clay. About 5 percent is organic matter, the decomposed remains of leaves, roots, and living things. The rest, close to half of the total, is empty space known as pore space, and in good soil that space is split about evenly between water and air, around 25 percent each. Those four parts, minerals, organic matter, water, and air, are the building blocks of every topsoil you will ever buy or dig.
The proportions shift with conditions, which is why the figures are approximate rather than fixed. After heavy rain the pores fill with water and the air fraction shrinks toward zero, which is why saturated soil feels heavy and airless. In a dry spell the reverse happens and air takes over the pore space. The mineral and organic fractions stay steadier because they are the solid skeleton of the soil, but even they vary: a sandy soil might be closer to 50 percent mineral with very little organic matter, while a rich garden loam might carry 8 to 10 percent organic matter after years of composting.
What makes this mix so useful for growing is the balance. The mineral particles give the soil its body and hold nutrients, the organic matter feeds plants and stores moisture, the water carries dissolved nutrients to roots, and the air lets roots and soil life breathe. Take any one part too far and the soil struggles: all sand and no organic matter drains too fast, all clay and no air suffocates roots. Understanding the four ingredients is the foundation for every other question in this guide, and it explains why the topsoil layer is treated as the most valuable part of the ground.
Topsoil composition breakdown
The table below lays out the four components of a typical healthy topsoil, the approximate share of total volume each one takes up, and the job it does. Think of these as round numbers for a well-balanced loam rather than exact measurements, since real soil shifts with weather, region, and how it has been managed.
| Component | Approx. share by volume | Role in the soil |
|---|---|---|
| Mineral particles (sand, silt, clay) | ~45% | Form the physical body of the soil, hold and release nutrients, and set the texture and drainage |
| Organic matter and humus | ~5% | Feeds plants and soil life, stores moisture, improves structure, and gives topsoil its dark color |
| Water | ~25% | Fills pore space, dissolves nutrients, and delivers them to plant roots |
| Air | ~25% | Fills the remaining pores so roots, microbes, and worms can breathe |
| Living organisms (microbes, worms, roots) | Small fraction of the total, huge in effect | Break down organic matter, recycle nutrients, and build soil structure |
Reading down the solids column, the mineral and organic parts add up to about half the soil, and the water and air make up the other half. That fifty-fifty split between solids and pores is the single most important idea about soil structure. When you compact soil by driving on it or working it wet, you crush the pore space, and the water and air have nowhere to go, which is why compacted ground grows plants so poorly. The living organisms in the bottom row barely register by weight, yet without them organic matter would never break down and nutrients would never cycle, so their effect on the soil is out of all proportion to their mass.
Sand, silt, and clay: the mineral skeleton
The mineral half of topsoil, that roughly 45 percent, is not one thing but a mixture of three particle sizes, and the ratio between them decides almost everything about how the soil behaves. Sand is the largest particle, gritty and visible to the eye, ranging from about 0.05 to 2 millimeters. Silt is medium-sized, smooth and floury when dry, slippery when wet, and far smaller than sand. Clay is the smallest of all, so fine that individual particles are invisible without a microscope, and it is clay that makes wet soil sticky and dry soil hard.
The blend of these three is what soil scientists call texture, and it is described using a soil texture triangle that names the result. A soil with a balanced mix of all three, and enough organic matter, is called loam, and it is the texture most gardeners want because it drains well while still holding moisture and nutrients. Lean heavily toward sand and you get a sandy soil that drains fast but dries out and loses nutrients quickly. Lean toward clay and you get a heavy soil that holds water and nutrients well but drains slowly and compacts easily. Most real topsoils fall somewhere in between, which is why you hear terms like sandy loam or clay loam.
You can get a rough read on your own soil’s texture with a jar test: put a few inches of soil in a clear jar, fill it with water, shake it hard, and let it settle for a day. The sand drops to the bottom first, silt settles in the middle, and clay forms the top layer, so the bands show you the rough proportions. This texture is baked into the soil and cannot really be changed, only improved with organic matter, which is why knowing what is in topsoil before you buy it matters so much. If you want to compare the ground blends sold for growing, the difference is covered in the guide comparing topsoil and garden soil.
Organic matter and humus: the living heart
Organic matter is only about 5 percent of topsoil by volume, but it does far more than that small share suggests, and it is the ingredient that separates true topsoil from lifeless subsoil or fill dirt. Organic matter is the remains of things that were once alive: fallen leaves, dead roots, spent plants, and the bodies of insects and microbes, all in various stages of decay. As it breaks down it passes through a coarse stage and ends up as humus, the dark, spongy, fully decomposed material that gives rich topsoil its near-black color and its earthy smell.
That small fraction of organic matter punches well above its weight for several reasons. It acts like a slow-release pantry, feeding plants and soil microbes as it decomposes and supplying much of the nitrogen a garden needs. It behaves like a sponge, holding many times its own weight in water, which helps sandy soils retain moisture through a dry week. It also glues mineral particles into crumbs, creating the loose, crumbly structure that lets air and water move freely and roots push through easily. A soil with healthy organic matter feels soft and breaks apart in your hand, while a soil stripped of it feels hard, pale, and dead.
Because organic matter is constantly being consumed by soil life, it needs topping up, which is why gardeners add compost, aged manure, or leaf mold year after year. This is also why the dark color of a soil is a useful, if imperfect, clue to its quality: darker usually means more organic matter, though some dark soils simply owe their color to certain minerals. The way this organic layer builds up over time is the subject of how topsoil is formed, and it explains why real topsoil takes centuries to develop naturally but can be enriched in your own beds within a season or two.
Once you know the blend you want, the article on how topsoil is formed and enriched shows how to build up organic matter, and the Dirt Calculator tells you how many cubic yards to order for the depth you have in mind.
Water and air: the half you cannot see
It surprises many people that about half of healthy topsoil is not solid material at all but empty space, called pore space, shared between water and air. In an ideal, well-structured soil that space is split roughly evenly, around 25 percent water and 25 percent air by volume, and keeping that balance is the difference between soil that grows things and soil that drowns or starves them.
The pores come in two useful sizes. Large pores, the gaps between bigger particles and soil crumbs, drain freely and stay full of air most of the time, which is what lets roots and soil organisms breathe. Small pores, the tiny spaces within and between fine particles, hold onto water by capillary action even after the soil has drained, acting as the reservoir that plants sip from between rains. A good soil has plenty of both, so it drains after a storm yet stays moist for days afterward. Sandy soils are almost all large pores, so they drain fast and dry out; clay soils are almost all small pores, so they hold water and can stay waterlogged.
This water-and-air balance is dynamic, shifting hour by hour with the weather. Right after heavy rain, water pushes the air out and fills nearly all the pore space, which is why plants can suffer in a flooded bed even though they need water: their roots are starved of oxygen. As the soil drains and dries, air moves back in. Roots need both, and the crumb structure built by organic matter and soil life is what keeps enough of each available. This is also the reason working or walking on wet soil is so damaging, since it collapses the pores and the soil loses its ability to hold air, a problem that touches directly on whether topsoil or a garden soil blend is the better choice for a given bed.
The living part: microbes, worms, and roots
Beyond the four measurable ingredients, topsoil is alive, and the living fraction is what turns a pile of weathered rock and dead leaves into a working system. A single teaspoon of healthy topsoil can hold billions of bacteria, along with miles of fungal threads, plus protozoa, nematodes, mites, and insects, all feeding on one another and on the organic matter. You cannot see most of this life, but it is the engine that keeps the soil fertile.
Earthworms are the members of this community you can actually see, and they are a reliable sign of good topsoil. As worms tunnel they swallow soil and organic matter, digest it, and leave behind castings that are richer in available nutrients than the surrounding soil. Their tunnels open channels that let water soak in and air reach deeper, and their constant mixing blends organic matter down into the mineral soil. A spadeful of soil with several worms in it is a spadeful of soil that is working the way it should.
The microbes do the chemical heavy lifting. Bacteria and fungi break organic matter down into humus and release the nitrogen, phosphorus, and other nutrients locked inside it into forms plant roots can absorb. Certain fungi, called mycorrhizae, actually partner with roots, extending their reach for water and nutrients in exchange for sugars from the plant. Fine plant roots weave through all of it, and as older roots die they add fresh organic matter and open more channels. This whole living network is why the question of nutrients is not just about what minerals are present but about whether the soil is biologically active enough to release them, which leads directly into the question of whether topsoil comes with fertilizer or nutrients in it.
What is screened topsoil, and how is it sieved?
When you shop for topsoil you will constantly see the words screened topsoil, and the term describes a processing step rather than a different material. Screened topsoil is ordinary topsoil that has been passed through a mesh screen to strain out the debris that natural ground is full of: rocks, stones, roots, sticks, clods, and clumps. What comes through the screen is a finer, more uniform, more consistent soil that is easier to spread, rake level, and plant into. Unscreened topsoil, sometimes called raw or unprocessed, is dug straight from the ground and still contains all of those larger bits.
The screening is usually done by tumbling or vibrating the soil over a steel mesh, and the size of the mesh openings decides how fine the finished product is. Common screen sizes run from about half an inch down to a quarter inch, sometimes finer. A half-inch screen removes stones and roots larger than that opening while letting through soil and small pebbles, and it produces a general-purpose landscape topsoil. A finer three-eighths or quarter-inch screen produces a smoother soil that is better for seeding a new lawn, topdressing, or filling seed trays, because there are fewer lumps to interfere with tiny roots. You may also see double-screened soil, which has been through the process twice for extra consistency.
What screening does not do is change the fundamental recipe of the soil. The sand, silt, clay, and organic matter are all still there in roughly the same proportions; screening just removes the oversized junk and breaks up clods so the material flows and spreads evenly. That uniformity is worth paying a little more for on jobs where a smooth, even finish matters, such as leveling a lawn or filling raised beds. For rough grading or filling a large low area, unscreened soil or even fill dirt is often fine and cheaper. Deciding how much of either to buy is where the Topsoil Calculator earns its keep.
Does topsoil have rocks, clay, and sand in it?
These three questions come up constantly, and the short answers are yes, yes, and yes, with some useful detail behind each. Topsoil naturally contains sand and clay because, as we have seen, those are two of the three mineral particle sizes that make up nearly half of it. Every topsoil has some sand and some clay in it; the only variable is how much. A soil described as sandy simply has a higher proportion of sand, and one described as heavy or clay-rich has more clay. There is no such thing as topsoil with no clay or no sand, because those particles are the mineral skeleton of the material.
Rocks are a different story, because whether topsoil has rocks in it depends on whether it has been screened. Natural, unscreened topsoil dug from the ground almost always contains stones, from small pebbles up to fist-sized rocks, along with roots and sticks. That is normal for soil straight out of the earth. Screened topsoil, by contrast, has had those rocks strained out through the mesh, so a good screened product should be largely free of stones bigger than the screen opening. If you buy soil sold as screened and still find it full of rocks, either it was screened through a coarse mesh or it was not truly screened, both of which are worth raising with the supplier.
So the practical guidance is this: expect sand and clay in every topsoil, expect rocks in unscreened soil, and expect few to no rocks in properly screened soil. If a stone-free finish matters, such as for a seedbed or a lawn, pay for screened. If you are filling a large area under turf or under other material, a few stones in unscreened soil rarely cause trouble and the lower price can be worth it. Either way, the mineral makeup underneath is the same blend of particles described earlier, and understanding that blend is really understanding what is in topsoil at all.
Does topsoil have minerals and nutrients in it?
Topsoil does contain minerals and nutrients, but the amount varies enormously from one source to the next, and this is where buyers are most often disappointed. The mineral particles themselves, the sand, silt, and clay, are ground-up rock and carry a base level of mineral nutrients like potassium, calcium, magnesium, and various trace elements, which are released slowly as the particles continue to weather. Clay in particular is good at holding onto nutrients and handing them to roots, one reason a little clay in a soil is a good thing.
The nutrients that matter most for fast plant growth, though, especially nitrogen, come mainly from the organic matter and the biological activity breaking it down, not from the mineral particles. A topsoil rich in dark organic matter and full of worms and microbes will have real, working fertility, releasing nitrogen and other nutrients as the organic matter decomposes. A topsoil that is mostly pale mineral particles with little organic matter can be low in available nutrients even though it technically contains minerals. This is why two loads of soil both sold as topsoil can perform completely differently in a garden.
The important thing to understand is that most bulk topsoil is not fertilized. It is a natural material, not a potting mix, so unless a product specifically says it has been amended or fertilized, you should assume it carries only its natural fertility and plan to add compost or fertilizer for hungry plants like vegetables. Some bagged and premium blends are enriched, but the plain screened topsoil that fills a dump truck usually is not. The full picture of what nutrients you can and cannot count on is spelled out in the companion article on whether topsoil has fertilizer or nutrients in it, which is worth reading before you rely on topsoil alone to feed a garden.
Does topsoil drain well or absorb water?
Whether topsoil drains well or holds water is one of the most practical questions you can ask about it, and the answer comes straight back to the mineral blend and the organic matter described earlier. Topsoil does both, in a sense: it absorbs and holds a portion of the water that reaches it while letting the excess drain away, and the balance between holding and draining depends entirely on the soil’s texture. A good loam is prized precisely because it strikes a middle balance, soaking up enough moisture to carry plants between rains while still draining freely enough that roots are not left sitting in water.
Sandy topsoil drains quickly because it is full of large pores, so water rushes straight through and the soil dries out fast. It rarely gets waterlogged, but it also struggles to stay moist and loses dissolved nutrients as water passes through. Clay-rich topsoil is the opposite: its tiny pores absorb and hold a great deal of water, so it stays wet for a long time and can become waterlogged or slow to drain after heavy rain. Neither extreme is ideal, and both can be improved by mixing in organic matter, which loosens clay to help it drain and adds sponge-like water holding to sand.
Organic matter is the quiet hero of drainage in either direction. Because humus holds many times its weight in water yet also builds the crumb structure that opens up drainage channels, adding compost to almost any soil improves how it handles water. If you are placing topsoil over a poorly draining base, such as heavy subsoil or compacted ground, remember that the layer beneath matters too, since water that drains through the topsoil still has to get away below. Working out how deep a layer to lay for good drainage and root room is exactly what the Dirt Calculator helps with, and understanding the base you are building on ties back to what topsoil is and where it sits in the ground.
What is actually in a bag of topsoil?
Here is the part of the topsoil story that catches the most people out: the material inside a bag labeled topsoil is not regulated the way you might hope, and what you actually get varies a lot by brand, region, and price. The word topsoil on a bag is a marketing term as much as a technical one, and because there is no strict national standard forcing a bag of topsoil to contain a set percentage of real surface soil, the contents range from excellent to disappointing.
At the better end, a bag of topsoil contains screened natural topsoil, sometimes blended with compost or sand to improve texture, and it performs much like the four-part mix this guide describes. At the lower end, especially with the cheapest bags, what is inside can be closer to reprocessed subsoil, a blend of whatever soil and fine material the producer had on hand, sometimes with sand, ground bark, or other fillers mixed in. Two bags from different brands sitting side by side on the same shelf can be quite different products, one dark and crumbly, the other pale, heavy, and lifeless. The best defense is to open a bag if you can, or to squeeze one and feel whether it is soft and crumbly or hard and claggy, and to read the description for words like screened, blended, or enriched.
For small jobs, filling a few pots, patching a lawn, or topping up a raised bed, bagged topsoil is convenient and the quality question is manageable because you are only handling a little of it. For anything larger, buying bulk screened topsoil from a local yard usually gives you both better value and a clearer idea of what you are getting, because you can often see the pile before it is loaded. To compare how many bags it would take to equal a bulk load, and to decide which route makes sense, run your area and depth through the Topsoil Calculator before you buy.
Screened topsoil weight and how to judge quality
Because moisture and composition drive weight, people often ask how much a yard of screened topsoil weighs, and the answer follows from what is in it. A cubic yard of screened topsoil generally weighs about 2,000 to 2,200 pounds when it is dry to slightly moist, which is close to a ton, and it can climb toward 2,500 to 2,700 pounds or more when it is wet or carries a lot of clay. Screened soil is often a touch lighter and fluffier than unscreened soil right after processing because screening removes dense rocks and introduces air, though once it settles and takes on normal moisture the difference narrows. If you want the full breakdown of soil weight by volume and moisture, the dedicated guide on how much a yard of topsoil weighs lays it all out with a chart.
Knowing the composition also gives you a checklist for judging quality before you buy. Color is the first clue: good topsoil is dark brown to near black from its organic matter, while pale, gray, or yellowish soil often means subsoil low in organic matter. Feel is the second: healthy topsoil is crumbly and breaks apart easily in your hand, not hard, powdery, or sticky like clay. Smell is a third, since rich soil has a fresh, earthy odor rather than a sour or chemical one. Signs of life, such as a few worms or visible bits of decomposed plant material, tell you the soil is biologically active.
Put those together and you can size up a load quickly. Ask the supplier whether the soil is screened and to what mesh, whether it has been blended with compost, and where it came from. Dark color, crumbly feel, earthy smell, and the odd worm point to soil that will grow things well, while pale, hard, odorless material is a warning sign whatever the label says. Match that judgment to the job, buy screened for fine work and something cheaper for bulk fill, and confirm the amount with the Dirt Calculator so the right soil arrives in the right quantity.
Frequently asked questions
What is topsoil made of?
Healthy topsoil is a blend of four ingredients by volume: roughly 45 percent mineral particles, meaning sand, silt, and clay ground down from rock; about 5 percent organic matter, the decayed remains of plants and animals that becomes dark humus; around 25 percent water; and around 25 percent air, both held in the pore spaces between particles. On top of that mix live billions of microbes, plus earthworms, fungi, insects, and plant roots. The mineral and organic parts form the solid body of the soil, while the water and air fill the gaps, and the balance between all of them is what lets topsoil support plant growth.
What is screened topsoil?
Screened topsoil is ordinary topsoil that has been passed through a steel mesh to strain out rocks, stones, roots, sticks, and clods, leaving a finer, more uniform material that is easier to spread and plant into. The screen size, often between a half inch and a quarter inch, decides how fine the result is: coarser screens make a general landscape soil, while finer screens make a smoother soil suited to seeding lawns or filling beds. Screening does not change the underlying recipe of sand, silt, clay, and organic matter; it only removes the oversized debris and breaks up lumps so the soil flows and levels evenly.
Does screened topsoil have rocks in it?
Properly screened topsoil should be largely free of rocks, because screening exists specifically to strain out stones, roots, and clods through a mesh. Small pebbles below the screen opening may still pass through, so screened soil is not always perfectly stone-free, but it should have no large rocks. If soil sold as screened is full of stones, it was either run through a very coarse mesh or was not truly screened, and that is worth raising with your supplier. Unscreened topsoil, dug straight from the ground, almost always contains rocks and roots, which is normal for raw soil and is the main reason people pay a little extra for screened.
Does topsoil have clay and sand in it?
Yes, every topsoil contains both sand and clay, because those are two of the three mineral particle sizes, along with silt, that make up nearly half of the soil by volume. The only thing that varies is the proportion. A sandy topsoil has a higher share of the larger sand particles and drains quickly, while a clay-rich topsoil has more of the tiny clay particles and holds water. A balanced blend of sand, silt, and clay, plus organic matter, is called loam and is the texture most gardeners want. There is no topsoil with zero sand or zero clay, since those particles form the mineral skeleton of the material.
Does topsoil have nutrients or minerals in it?
Topsoil contains minerals and nutrients, but the amount varies widely by source. The mineral particles carry a base level of nutrients like potassium, calcium, and magnesium, released slowly as the rock weathers, and clay in particular holds nutrients for roots. The nutrients that drive fast growth, especially nitrogen, come mainly from organic matter and the microbes breaking it down, so a dark, organic-rich soil has real fertility while a pale mineral soil may be low in available nutrients. Most bulk topsoil is not fertilized, so unless a product says it is amended or enriched, plan to add compost or fertilizer for hungry plants like vegetables.
Does topsoil drain well or absorb water?
Topsoil does both: it absorbs and holds some water while letting the excess drain away, and the balance depends on its texture. Sandy topsoil is full of large pores, so it drains fast and dries out quickly. Clay-rich topsoil has tiny pores that hold a lot of water, so it stays wet and can become waterlogged. A balanced loam sits in the middle, holding enough moisture to carry plants between rains while draining freely enough to keep roots from drowning. Organic matter improves drainage either way, loosening clay so it drains and adding water-holding sponge to sand, which is why adding compost helps almost any soil.
How much does 1 yard of screened topsoil weigh?
A cubic yard of screened topsoil usually weighs about 2,000 to 2,200 pounds when dry to slightly moist, which is close to one ton, and it can rise toward 2,500 to 2,700 pounds or more when the soil is wet or carries a lot of clay. Freshly screened soil is often a little lighter and fluffier than unscreened soil because screening removes dense rocks and mixes in air, but once it settles and takes on normal moisture the weight is close to ordinary topsoil. Moisture is the biggest single factor, since water fills the pore spaces and adds several hundred pounds per yard without changing the volume.
What is actually inside a bag of topsoil?
It varies more than most people expect, because the word topsoil on a bag is loosely regulated and the contents range from excellent to poor. Better bags hold screened natural topsoil, sometimes blended with compost or sand, and behave like the four-part mineral and organic mix real topsoil should. Cheaper bags can be closer to reprocessed subsoil or a blend of whatever fine material the producer had, occasionally with fillers like bark or sand. Two brands on the same shelf can be quite different, so it helps to feel a bag for a soft, crumbly texture and to look for words like screened, blended, or enriched. For larger jobs, bulk soil from a local yard is usually better value and easier to inspect.
The quick version
Topsoil is a blend of four ingredients by volume: about 45 percent mineral particles of sand, silt, and clay, roughly 5 percent organic matter and humus, and close to half pore space split between water and air at about 25 percent each, plus billions of microbes, worms, and roots that make it live. The sand-silt-clay ratio sets the texture and drainage, organic matter supplies fertility and structure, and the water and air balance keeps roots alive. Screened topsoil is simply this same material sieved through a mesh to strain out rocks, roots, and clods. Every topsoil contains sand and clay, unscreened soil contains rocks, and most bulk topsoil is not fertilized, so dark, crumbly, earthy-smelling soil with a few worms is the sign of real quality.
For related reading, see what topsoil is and why it matters, whether topsoil has fertilizer or nutrients, and how topsoil is formed. Work out how much you need with the Dirt Calculator or Topsoil Calculator, browse more guides in the topsoil blog and the home calculators hub, or explore all the free tools on the Waldev homepage.
Disclaimer: This guide is for general planning and education only. Topsoil weight, coverage, and prices vary widely with moisture, soil type, region, and supplier, so treat every figure here as a starting estimate rather than an exact value. For a firm quantity, measure your own area and confirm the number with the Dirt Calculator; for a firm price, get a local quote before ordering.
USDA Natural Resources Conservation Service explains soil composition, texture, and the mineral and organic components that make up soil. NRCS soils →
University extension resources describe the sand, silt, and clay fractions and how their ratio determines soil texture and behavior. Soil texture and health →