A cap and a floor are mirror-image derivatives. Both are options on interest rates. Both are priced using the same Black-76 model. Both pay the holder when their respective threshold is breached. But they serve completely opposite purposes, are bought by completely different parties, and are combined into a collar structure that most borrowers never encounter until they’re trying to reduce an expensive cap premium. This guide explains both instruments clearly and shows how they interact.
In This Guide
Caps, floors, and collars explained from first principles through practical application.
Cap and Floor: The Basic Concepts
Before comparing the two instruments, it helps to have clean, precise definitions for each. Borrowers are typically familiar with caps from their loan requirements — floors are less commonly encountered but follow the exact same structural logic in reverse.
Definition: An option that pays the holder when a floating reference rate rises above a specified strike (the cap rate). The buyer pays an upfront premium and receives Max(Rate − Strike, 0) × Notional × Accrual Fraction for each period.
Protects against: Rates rising too high. The holder’s effective maximum rate is the cap strike.
Expires worthless when: Rates stay below the strike throughout the term.
Primary users: Floating-rate borrowers (especially bridge loan borrowers) who need protection against rate increases.
Definition: An option that pays the holder when a floating reference rate falls below a specified strike (the floor rate). The buyer pays an upfront premium and receives Max(Strike − Rate, 0) × Notional × Accrual Fraction for each period.
Protects against: Rates falling too low. The holder’s effective minimum rate is the floor strike.
Expires worthless when: Rates stay above the strike throughout the term.
Primary users: Floating-rate lenders and investors who receive floating income and need protection against rate decreases.
💡 The mirror relationship: A cap is a call option on an interest rate (bets on rates going up). A floor is a put option on an interest rate (bets on rates going down). For every cap buyer, there is a cap seller. For every floor buyer, there is a floor seller. In a collar structure, a borrower buys a cap and simultaneously sells a floor — becoming both a cap buyer and a floor seller in the same transaction.
Payoff Profiles: Visualising the Difference
The clearest way to understand how caps and floors differ is to look at their payoff profiles across different rate scenarios — and then see how a collar structure changes that profile into a bounded range.
The cap payoff profile
A cap has an asymmetric, one-sided payoff. Below the strike, the cap generates zero payments — it is dormant. Above the strike, the cap generates a payment that increases linearly with the rate. There is no theoretical upper limit to how much the cap can pay (though in practice rates have bounded ranges). The premium you paid upfront is the maximum loss; the settlement payments are the gains. This is exactly the structure a borrower wants: downside is limited and known (the premium), upside protection is unlimited.
Cap settlement per period = Notional × Max(SOFR − Cap Strike, 0) × Accrual Fraction
If SOFR = 4.00%, Strike = 5.00%: Settlement = $15M × Max(-1.00%, 0) × (1/12) = $0
If SOFR = 5.50%, Strike = 5.00%: Settlement = $15M × 0.50% × (1/12) = $6,250
If SOFR = 6.50%, Strike = 5.00%: Settlement = $15M × 1.50% × (1/12) = $18,750
The floor payoff profile
A floor has the exact mirror profile. Above the strike, the floor generates zero payments — it is dormant. Below the strike, the floor generates a payment that increases linearly as rates fall further below the strike. For the floor buyer, this provides income protection when rates are low. For the floor seller (such as a borrower who sells a floor as part of a collar), this creates a payment obligation when rates fall — a position that benefits from rates staying high and is harmed by rates falling.
Floor settlement per period = Notional × Max(Floor Strike − SOFR, 0) × Accrual Fraction
If SOFR = 5.50%, Strike = 4.00%: Settlement = $15M × Max(-1.50%, 0) × (1/12) = $0
If SOFR = 3.50%, Strike = 4.00%: Settlement = $15M × 0.50% × (1/12) = $6,250
If SOFR = 2.50%, Strike = 4.00%: Settlement = $15M × 1.50% × (1/12) = $18,750
The collar payoff profile
When a borrower buys a cap and sells a floor simultaneously, the two payoff profiles combine. The cap provides protection above the cap strike. The sold floor creates an obligation below the floor strike. Between the two strikes, neither pays — the borrower just pays the floating rate. The result is a bounded effective rate range.
Who Buys Caps vs. Who Buys Floors
The cap and floor markets serve fundamentally different clienteles because the two instruments address opposite economic problems. Understanding who uses each instrument — and why — clarifies why commercial real estate borrowers almost always deal with caps (and occasionally sell floors) but rarely buy floors outright.
🟢 Cap Buyers
- Floating-rate borrowers with bridge loans, construction loans, or agency ARM products
- Corporate borrowers with floating-rate credit facilities who need income statement protection
- Real estate equity investors whose deal underwriting is sensitive to rate increases
- CLO equity holders who want protection against their floating-rate liabilities rising
- Any entity that pays a floating rate and needs a cost ceiling
🔵 Floor Buyers
- Floating-rate lenders (banks, debt funds) who receive floating income and want a minimum yield guarantee
- Investors in floating-rate bonds, CLO debt tranches, and ABS that receive SOFR-indexed coupons
- Insurance companies with floating-rate investment portfolios seeking income certainty
- Any entity that receives a floating rate and needs an income floor
- Borrowers in collar structures who sell (rather than buy) floors to offset cap premium cost
Why CRE borrowers almost never buy floors outright
Commercial real estate borrowers pay floating-rate interest — they don’t receive it. A floor protects against rates falling, which is actually a benefit for borrowers (lower rates mean lower interest expense). A borrower who purchased a floor would be paying premium to protect against a scenario that helps them — an economically irrational use of capital. The only reason a CRE borrower touches a floor derivative is when they sell one as part of a collar to offset cap premium cost — in which case they are accepting the obligation to pay the dealer if rates fall below the floor strike, in exchange for a premium that reduces their upfront cap cost.
Settlement Mechanics: Cap vs. Floor in Practice
Both caps and floors are settled periodically — monthly, quarterly, or semiannually depending on the reset frequency specified in the confirmation. The settlement calculation is symmetric: where the cap pays when the reference rate exceeds the strike, the floor pays when the reference rate falls below the strike.
| SOFR Level | Cap Settlement (5.00% Strike) | Floor Settlement (3.50% Strike) | Collar Net Position (Cap 5.00%, Floor 3.50%) |
|---|---|---|---|
| 2.50% (rates very low) | $0 — cap dormant | +$12,500 received | −$12,500 paid (floor obligation) |
| 3.00% (rates low) | $0 — cap dormant | +$6,250 received | −$6,250 paid (floor obligation) |
| 3.50% (at floor strike) | $0 — cap dormant | $0 — floor at strike | $0 — both dormant |
| 4.25% (middle range) | $0 — cap dormant | $0 — floor dormant | $0 — both dormant |
| 5.00% (at cap strike) | $0 — cap at strike | $0 — floor dormant | $0 — both dormant |
| 5.75% (rates elevated) | +$9,375 received | $0 — floor dormant | +$9,375 received (cap active) |
| 6.50% (rates high) | +$18,750 received | $0 — floor dormant | +$18,750 received (cap active) |
Illustrative monthly settlements on $15M notional. Cap strike 5.00%, Floor strike 3.50%, monthly accrual (1/12). Collar net = cap receipts minus floor payments (from borrower’s perspective as collar buyer/floor seller).
⚠️ Note for collar borrowers: In the table above, when SOFR is 2.50%, the collar borrower owes $12,500 to the dealer as a floor obligation — it does not appear in their bank account as a receipt. This cash outflow in a low-rate environment is the tradeoff for the premium savings the collar structure provides upfront. Make sure your deal model accounts for this potential cash flow in a rate-fall scenario.
How Caps and Floors Are Priced: The Symmetric Model
Caps and floors are both priced using the Black-76 model. The cap uses a series of call options (caplets) on forward rates. The floor uses a series of put options (floorlets) on the same forward rates. The inputs are the same — notional, strike, term, implied volatility, forward rate, discount factor — and the mathematics are parallel.
Caplet Value = N × τ × DF × [F × N(d₁) − K × N(d₂)]
Floorlet Value = N × τ × DF × [K × N(−d₂) − F × N(−d₁)]
Where d₁ and d₂ are the same as in the caplet formula:
d₁ = [ln(F/K) + (σ²/2)×T] / (σ×√T)
d₂ = d₁ − σ×√T
Note that: N(−d₁) = 1 − N(d₁) and N(−d₂) = 1 − N(d₂)
This means caplets and floorlets share the same d₁ and d₂ values —
only the formula structure changes (call vs. put option payoff).
Relative cost: cap vs. floor at the same strike
Given the same notional, term, and strike, a cap and a floor do not necessarily cost the same amount. Their relative cost depends on where the forward rate curve sits relative to the strike — the same logic that determines whether a cap is in-the-money or out-of-the-money applies to floors in reverse.
| Scenario | Forward Rate | Strike | Cap Moneyness | Floor Moneyness | Relative Cost |
|---|---|---|---|---|---|
| High-rate environment | 5.80% | 5.00% | Cap is ITM — expensive | Floor is OTM — cheap | Cap costs much more than floor at same strike |
| Symmetric environment | 5.00% | 5.00% | Cap is ATM | Floor is ATM | Cap and floor cost similar amounts (put-call parity) |
| Low-rate environment | 3.50% | 5.00% | Cap is OTM — cheap | Floor is ITM — expensive | Floor costs much more than cap at same strike |
This asymmetry in relative cost is crucial for understanding collar structures. In a high-rate environment — exactly when cap premiums are most expensive for borrowers — floors at rates meaningfully below current forward rates are cheap. The premium received from selling a cheap OTM floor partially offsets the expensive cap premium, but the floor’s cheapness means the offset is modest. In a low-rate environment, selling a floor is more lucrative (the floor is more in-the-money relative to forward rates), but caps are cheap anyway, reducing the incentive for the collar trade.
Put-Call Parity for Interest Rates: The Mathematical Relationship
The cap and floor on the same notional, strike, and term are linked by a mathematical relationship called put-call parity. In equity options, put-call parity links the price of a call and put at the same strike. In interest rate derivatives, the equivalent relationship links cap and floor prices to the value of an interest rate swap.
Cap − Floor = Swap (pay fixed at the strike, receive floating)
Equivalently:
Cap Price − Floor Price = PV of (Forward Rate − Strike) over the term
Or expressed as a swap:
Buying a cap and selling a floor (same notional, same strike, same term)
= economically equivalent to entering a pay-fixed interest rate swap at the strike
This means: a collar (long cap + short floor) at the same strike as a swap rate
costs exactly zero (zero-cost collar at the swap rate), because the
cap premium and floor premium offset exactly.
What put-call parity tells us about collar structures
Put-call parity reveals something important about collar design: if you set both the cap strike and the floor strike equal to the current at-the-money swap rate, the collar has zero net premium — the floor sale exactly offsets the cap purchase. This is the theoretical basis for the zero-cost collar. In practice, the cap and floor strikes in a zero-cost collar are usually different from each other (the cap is set at one level, the floor at another) to achieve a specific balance of protection and premium offset.
The parity relationship also explains why lenders sometimes use language like “the cap cost can be reduced by selling a floor” — they are implicitly referencing the put-call parity that links the two instruments. A borrower who understands this can engage in a more informed discussion with their derivatives advisor about where to set the floor strike to achieve a desired premium reduction without taking on unacceptable floor exposure.
The Collar: Combining Cap and Floor to Reduce Cost
A collar is the practical application of the cap-floor relationship for borrowers who want cap protection but need to reduce the upfront premium cost. The borrower buys a cap (ceiling protection) and simultaneously sells a floor (accepting a payment obligation if rates fall below the floor strike). The premium received from selling the floor offsets part or all of the cap premium.
Why collars make sense in certain environments
A collar makes financial sense when three conditions are met simultaneously. First, the cap premium is high enough that it strains deal economics or equity returns. Second, the floor strike can be set at a level that is genuinely unlikely to be breached during the loan term — meaning the borrower is selling protection against a scenario they consider improbable. Third, the lender approves the collar structure, which is not automatic — lenders must review and accept the added floor obligation.
The premium arithmetic
Suppose a borrower needs a cap on $18M at a 5.25% strike for 2 years, and the cap dealer quotes $256,000 in an elevated vol environment. The borrower’s advisor prices a floor at a 3.50% strike on the same terms — in a market where the forward curve is well above 3.50%, this floor is deeply out-of-the-money and costs only $38,000. Selling that floor returns $38,000 to offset the cap premium, reducing the net cost to $218,000 — a 15% reduction. The tradeoff: if SOFR falls below 3.50% at any point, the borrower owes monthly payments to the dealer.
Setting the floor strike correctly
The floor strike should be set at a level that is both meaningfully below the current forward curve and below the level at which your deal can comfortably absorb the additional payment obligation. A floor at 2.00% when SOFR is at 4.80% produces very cheap floor premium but provides almost no scenario where the obligation is triggered. A floor at 4.00% when SOFR is at 4.80% is more expensive but creates a meaningful probability that the floor will be triggered — turning the borrower into a net payer in a rate-fall environment.
Position: Long a cap at 5.25% (bought) + Short a floor at 3.75% (sold)
Net premium: Cap premium paid − Floor premium received = Net upfront cost (less than standalone cap)
When SOFR > 5.25%: Cap pays borrower. Net: effective rate capped at 5.25%.
When 3.75% ≤ SOFR ≤ 5.25%: Neither instrument pays. Borrower pays current floating rate.
When SOFR < 3.75%: Borrower pays dealer the floor settlement. Net: effective rate floored at 3.75% (borrower cannot benefit from rates below 3.75%).
The trade-off in one sentence: The borrower surrenders the benefit of rates falling below 3.75% in exchange for a reduced upfront cost of cap protection above 5.25%.
The Zero-Premium Collar: When the Cost Is Eliminated Entirely
A zero-premium (or zero-cost) collar is a collar structure where the floor strike is set at precisely the level that makes the floor premium equal to the cap premium — resulting in a net premium of zero. The borrower pays nothing upfront but gives up all benefit of rates falling below the floor strike.
How to find the zero-cost floor strike
To structure a zero-cost collar, the derivatives advisor iteratively adjusts the floor strike until the floor’s premium matches the cap’s premium exactly. Starting with a floor strike far below current forward rates (very cheap floor, large net cap cost remaining) and moving it progressively higher (more expensive floor, reducing net cost) until the floor premium equals the cap premium, the zero-cost floor strike is found.
| Floor Strike (on $18M, 2yr) | Floor Premium | Cap Premium (5.25% strike) | Net Premium | Probability Floor Triggered |
|---|---|---|---|---|
| 2.00% | $8,000 | $256,000 | $248,000 still owed | Very low |
| 3.00% | $28,000 | $256,000 | $228,000 still owed | Low |
| 3.75% | $52,000 | $256,000 | $204,000 still owed | Moderate-low |
| 4.30% | $116,000 | $256,000 | $140,000 still owed | Moderate |
| ~4.65% | $256,000 | $256,000 | $0 — zero-cost collar | Moderate-high |
Illustrative. Actual floor strikes and premiums depend on current market conditions. Zero-cost floor strike in this example is approximately 65bps below current SOFR of ~4.30% — meaning rates only need to fall 65bps to trigger the floor obligation. This is not a remote scenario.
🚨 The zero-cost collar danger zone: The zero-cost collar is seductive because of its $0 upfront cost — but it is rarely as attractive as it sounds in practice. To eliminate the cap premium entirely, the floor strike must be set close to current rates — and in the example above, a 65bp rate decline triggers the obligation. In a business cycle where rates can move 200–300bps, that is not a remote scenario. Borrowers who choose a zero-cost collar primarily to avoid the cap premium often discover that the floor obligation materialises at exactly the moment they were hoping to benefit from lower rates.
The collar decision starts with knowing what the cap actually costs. Use the Waldev cap calculator to get your standalone cap premium. That number is your baseline — the collar can reduce it, but you need to understand the base case first. If the standalone cap premium is $180,000 but doesn’t materially impair your deal returns, a collar’s premium savings may not be worth the floor obligation risk.
Loan SOFR Floor vs. Floor Derivative: An Important Distinction
One source of genuine confusion among commercial real estate borrowers is the distinction between two types of “floor” that appear in their loan documentation — the contractual SOFR floor in the loan agreement itself, and a floor derivative purchased from a dealer. These look similar on the surface but are structurally, legally, and economically different instruments.
Loan Agreement SOFR Floor
What it is: A contractual provision in the loan itself specifying a minimum reference rate. Example: “The Applicable Rate shall be the greater of 1-Month Term SOFR and 0.50% per annum.” The loan charges at least 0.50% SOFR regardless of where market SOFR trades.
Who benefits: The lender. The floor ensures the lender earns at least a minimum floating rate on the loan even if SOFR falls to near-zero levels.
Who is harmed: The borrower. If SOFR falls below the floor, the borrower pays more than market rates on the loan.
Legal nature: A term of the loan agreement. No separate ISDA documentation. No upfront premium — it is embedded in the loan pricing.
Floor Derivative (Financial Instrument)
What it is: A separate financial contract between two parties (borrower/buyer and dealer) documented under an ISDA Master Agreement. The buyer pays an upfront premium and receives cash payments when SOFR falls below the floor strike.
Who benefits: The floor buyer (typically the lender, or a floating-rate investor). The floor buyer receives income protection when SOFR is low.
Who is harmed: The floor seller. When SOFR falls below the strike, the seller makes payments to the buyer — an obligation that erodes the seller’s benefit from low rates.
Legal nature: A derivatives contract. Requires ISDA Master Agreement. Has an upfront premium (if buyer) or premium receipt (if seller).
| Characteristic | Loan SOFR Floor | Floor Derivative |
|---|---|---|
| Where it appears | Loan agreement / credit agreement | Separate ISDA confirmation |
| Who sets the terms | Lender (in the loan negotiation) | Negotiated with dealer bank |
| Upfront premium | None — embedded in loan pricing | Yes — paid by buyer to seller |
| Cash flows | Higher interest payments to lender | Periodic cash settlement payments |
| Legal framework | Loan documentation | ISDA Master Agreement + confirmation |
| Can be sold/terminated? | No — it is a loan term | Yes — like any derivative |
💡 Watch for loan SOFR floors when evaluating collar structures. If your loan has a contractual SOFR floor of 1.50% and you sell a floor derivative at 3.75%, your exposure to rates falling below 1.50% is already partially hedged by the loan floor — but the floor derivative still obligates you to pay settlements to the dealer for rates between 1.50% and 3.75%. This interaction between the loan floor and the sold floor derivative can create complexity in your effective rate calculation.
Three Rate Scenarios: Cap vs. Floor vs. Collar on the Same Loan
This worked comparison shows how the same $16M floating-rate loan performs under a standalone cap, a standalone floor (hypothetical — shown for comparison only), and a collar structure across three rate environments.
Loan and structure parameters
$16M loan at SOFR + 3.00%. Cap at 5.25% strike (premium: $210,000). Floor at 3.50% strike (premium if bought: $36,000; if sold: receive $36,000). Collar = buy cap at 5.25% + sell floor at 3.50%, net premium: $174,000.
💡 The scenario table shows the collar’s key trade-off clearly: in a rising rate scenario it performs identically to the standalone cap but at lower upfront cost. In a falling rate scenario, it loses the benefit of the lower rate environment. Whether that trade-off is acceptable depends entirely on how likely the borrower believes a significant rate decline is during their loan term.
Frequently Asked Questions
What is an interest rate floor?
An interest rate floor is a derivative that pays the holder whenever a floating reference rate falls below a specified floor rate. The floor buyer pays an upfront premium and receives the difference between the floor rate and actual SOFR for each period when SOFR is below the floor. Floors are the mirror image of caps: caps protect against rates rising above a ceiling; floors protect against rates falling below a floor. The primary buyers are lenders and floating-rate investors who receive SOFR-indexed income and need protection against that income being reduced by rate declines.
Who typically buys interest rate floors?
Floors are primarily purchased by entities that receive floating-rate income: lenders who originate floating-rate loans, investors in floating-rate bonds and CLO debt tranches, and insurance companies with floating-rate investment portfolios. Commercial real estate borrowers — who pay rather than receive floating rates — rarely buy floors outright. The exception is when a borrower sells a floor as part of a collar structure to offset cap premium cost; in this case they are accepting the payment obligation of a floor seller rather than purchasing floor protection.
What is a collar and how does it reduce cap cost?
A collar combines a purchased cap and a sold floor on the same notional and term. The borrower buys a cap (receiving protection above the cap strike) and simultaneously sells a floor (accepting an obligation to pay when rates fall below the floor strike). The premium received from selling the floor offsets part or all of the cap premium. The result is a lower upfront cost in exchange for giving up the benefit of rates falling below the floor strike. For example, selling a floor at 3.50% when SOFR is at 4.60% generates modest premium (the floor is OTM) that partially reduces an expensive cap premium.
When should a borrower consider a collar over a standalone cap?
A collar makes sense when: the cap premium is materially straining deal economics, the floor strike can be set at a level genuinely unlikely to be breached during the loan term, the deal’s borrower can absorb the floor obligation if rates do fall (it won’t create a cash flow crisis), and the lender approves the collar structure. A zero-cost collar is attractive in theory but dangerous in practice because eliminating the cap premium requires setting the floor close to current rates — creating a high probability the floor will be triggered and the borrower will make payments to the dealer.
Is a loan SOFR floor the same as a floor derivative?
No — they are entirely different instruments. A loan SOFR floor is a contractual provision in the loan agreement itself, setting a minimum reference rate for interest calculation. It is an embedded loan term, benefits the lender, and requires no ISDA documentation. A floor derivative is a separate financial contract documented under an ISDA Master Agreement between two parties, with an upfront premium and periodic cash settlements. The loan floor is a term of your debt; the floor derivative is a separate financial product. Both can appear in the same deal independently.
Do floors and caps always cost the same at the same strike?
No — a cap and floor at the same strike cost different amounts unless the forward curve happens to be symmetric around that strike (which is rare). In a high-rate environment where the forward curve is above the strike, a cap at that strike is in-the-money (expensive) while a floor at the same strike is out-of-the-money (cheap). The mathematical relationship between cap and floor prices is governed by put-call parity: Cap − Floor = Swap value, where the swap is pay-fixed at the strike. This relationship means you can always derive the theoretical floor price if you know the cap price and the relevant swap rate.
Can a borrower profit from selling a floor?
A borrower who sells a floor receives an upfront premium — a cash inflow. If rates stay above the floor strike throughout the term, no payments are made and the borrower keeps the full premium — a positive outcome. If rates fall below the floor strike, the borrower must make periodic payments to the dealer for as long as rates remain below the strike — a negative outcome. Whether the net position is profitable depends on the magnitude and duration of any rate decline versus the premium received. The floor sale is not a guaranteed profit — it is a position that benefits from rates staying high and is harmed by rates falling significantly.
Start With the Cap Premium Before Evaluating a Collar
The collar decision — whether to sell a floor to offset cap cost — starts with knowing exactly what the standalone cap costs. Without that baseline, you cannot evaluate whether the premium savings from the collar are worth the floor obligation you’re accepting.
The Waldev interest rate cap calculator gives you that baseline. Enter your deal’s notional, strike, term, and current market inputs to generate an independent cap premium estimate. Once you have that number, you can evaluate collar structures by asking: is the premium reduction from selling a floor at various strike levels worth giving up the benefit of rates falling to those levels?
Calculate My Cap Premium →More financial tools at Waldev finance tools.
Disclaimer: This article is for educational and informational purposes only. All premium estimates, settlement calculations, and scenario comparisons are illustrative and hypothetical. Interest rate caps, floors, and collar structures are financial derivatives with complex legal documentation requirements — they should be purchased only with the guidance of a qualified derivatives advisor. This article does not constitute financial, legal, or derivatives advisory advice. Collar structures involving sold floors create payment obligations that must be carefully evaluated relative to deal cash flows and lender approval requirements before execution.
