Interest rate cap cost is the one-time premium a borrower pays for a cap, and it is set by where the strike sits against the SOFR forward curve, the term, the notional and implied volatility; its intrinsic part can be estimated from the forward curve before any dealer is asked for a quote. Estimate it early. A cap bought against a closing or extension deadline is bought at whatever the market charges that week, and the borrower has no time to change the strike or the term.
What sets the price of a cap
A cap is a strip of caplets, one for each reset period of the loan. Each caplet pays if SOFR for its period settles above the strike. In the options literature, caplets are treated as options on the forward interest rate for their period and are valued with an option model, classically the Black (1976) formula, with implied volatility as the input the market quotes. The premium is the sum of the caplets. See interest rate cap for the payment mechanics.
That structure explains each driver.
Strike against the forward curve. Where the SOFR forward curve runs above the strike, the caplet is expected to pay, and the buyer pays for that expected payment in full, upfront. This is the intrinsic part of the premium, and it is usually the largest part for a strike well below the curve.
Term. A longer cap has more caplets, and the later ones carry more uncertainty, so each added year usually costs more than the one before it when the curve is flat or rising.
Notional. Premium scales with notional. A cap on $50 million costs about twice a cap on $25 million at the same terms. A notional that steps down with the loan’s amortization costs less than a flat one.
Implied volatility. The market’s price for how far SOFR may move away from the curve, which sets the value of the chance that SOFR ends above the strike in periods where the curve says it will not. This is the time value in the premium, and it is what makes an out-of-the-money cap cost anything at all. The market dynamics are covered in caps in your debt portfolio.
Index and reset. The cap should settle on the same SOFR and reset dates as the loan: a cap on 1-month Term SOFR does not hedge a loan on 30-day Average SOFR exactly. Freddie Mac’s Optigo floating-rate loans, for example, are priced off 30-day Average SOFR, and the borrower may buy its cap from a third-party provider on Freddie Mac’s approved counterparties list. The quote also includes the dealer’s margin, which competing quotes narrow.
Estimating cap cost from the forward curve
The forward curve comes from SOFR futures and swap prices, which imply a rate for each future period. The intrinsic value of a cap is the sum of each caplet’s expected payment on that curve: forward SOFR minus the strike, when positive, times notional, times the fraction of the year. Discounted to today, it sets a floor under a fair quote.
Illustrative example: expected payments on a $25 million, two-year cap with quarterly resets, on an invented forward curve (each quarter counted as 0.25 of a year, undiscounted)
| Quarter | Forward SOFR | 3.50% strike | 4.00% strike | 4.50% strike |
|---|---|---|---|---|
| 1 | 3.80% | $18,750 | $0 | $0 |
| 2 | 3.90% | $25,000 | $0 | $0 |
| 3 | 4.10% | $37,500 | $6,250 | $0 |
| 4 | 4.25% | $46,875 | $15,625 | $0 |
| 5 | 4.40% | $56,250 | $25,000 | $0 |
| 6 | 4.50% | $62,500 | $31,250 | $0 |
| 7 | 4.50% | $62,500 | $31,250 | $0 |
| 8 | 4.60% | $68,750 | $37,500 | $6,250 |
| Intrinsic value | $378,125 | $146,875 | $6,250 |
Each cell is (forward SOFR minus strike) x $25,000,000 x 0.25. Quarter 8 at the 4.00% strike: 0.60% x $25,000,000 x 0.25 = $37,500. Discounting each payment to today would lower the totals slightly.
Reading the table. Moving the strike from 4.00% to 3.50% adds $231,250 of expected payments; moving it to 4.50% removes $140,625. The 4.50% cap shows almost no intrinsic value, so nearly its whole premium is time value, which is why out-of-the-money caps move most, in proportion, when volatility changes.
Term. Cut the 4.00% cap to four quarters and its intrinsic value falls to $21,875. The second year carries $125,000 of the $146,875, because the curve rises through it.
Dealer quotes. Suppose a dealer quotes the 4.00% cap at $260,000. The quote is $113,125 above undiscounted intrinsic value: that is the time value and the dealer’s margin. A quote below the discounted intrinsic value would be a mispricing or a sign the curve has moved; a quote far above it says implied volatility is high or the dealer’s margin is wide, which is a reason to get competing quotes and test a different strike or term before buying.
Using a rate cap calculator
A rate cap calculator, whether a spreadsheet, a pricing tool or a dealer’s indication, gives an estimate that is only as good as its inputs. Gather these before running one:
- Notional schedule, matched to the loan balance by period, including amortization and future funding.
- Strike, and the strike the loan documents allow or require.
- Start and end dates, including any gap to the next extension date.
- Index and reset frequency, matched to the loan.
- Forward curve and implied volatility on the pricing date, with the date recorded.
- Counterparty requirements from the loan documents, such as a minimum rating.
The estimate is for budgeting and for testing quotes. The price is what a qualifying counterparty will trade at on the day.
Replacement cap cost at extension
A replacement cap is priced on the day it is bought, at that day’s curve and volatility, for the strike and term the loan requires then. The original premium tells you almost nothing about it. Extension terms often tighten the strike, and a tighter strike against a higher curve raises the premium on both counts. See bridge and debt fund extension tests.
Lenders manage this risk with escrows. Freddie Mac’s cap options sheet for floating-rate cash loans (May 2025) sets out one version. The borrower may choose an initial cap term of 2, 3 or 4 years. The replacement cap escrow is sized at 125% of the lender’s estimated replacement cost for 2- and 3-year initial caps and 100% for 4-year caps, where the estimate covers a replacement cap running to the earlier of two years after the existing cap ends or loan maturity. With a 2-year initial cap, at least 50% of the estimated cost of the first replacement is collected at origination. Escrows are analyzed semi-annually, and replacement caps run at least one year, in annual increments.
Illustrative example: a replacement cap escrow sized on those rules for a 2-year initial cap (invented cost estimates)
| Point | Lender’s estimated replacement cost | Escrow target at 125% | Note |
|---|---|---|---|
| Origination | $180,000 | $225,000 | At least $90,000 collected at closing (50% of $180,000) |
| Semi-annual review, curve and volatility higher | $260,000 | $325,000 | Target rises $100,000 |
| Semi-annual review, curve and volatility lower | $150,000 | $187,500 | Target falls $37,500 from origination |
Other lenders size escrows differently, and Freddie Mac’s terms are subject to change; read the loan documents. The pattern holds generally: the escrow follows the market, so the borrower’s cash commitment moves every review. The requirement side is covered in hedge requirements, replacement caps and mark-to-market.
What to track
- Premium estimate for every cap and every future replacement, repriced on the current curve on a set schedule.
- Strike against the forward curve, by period, so it is clear which caplets carry the value.
- Escrow balance against the lender’s current estimate, and the date of the next escrow review.
- Replacement deadlines against extension dates and loan maturity.
- Mark-to-market of caps in place, which is residual value at a sale or refinancing. See hedge mark-to-market.
- Aggregate replacement cost by quarter across the portfolio, so a cluster of expiries shows up in the budget before it shows up as a capital call.
How this looks in LoanBoss
Hedge requirements are tracked with live mark-to-market values and replacement cap costs, so the budget for each replacement reflects current pricing. Hedges carry real-time rates and precise settlement calculations for reconciliation. Replacement caps and extension notices are tracked as critical dates with alerts, alongside the loan’s other obligations from the abstract.
Frequently Asked Questions
How much does an interest rate cap cost?
It depends on the strike against the forward curve, the term, the notional and volatility on the day of purchase, so any single figure goes stale quickly. Estimate intrinsic value from the forward curve, then compare dealer quotes against it.
Why does a replacement cap cost more than the original?
It is priced at the curve, volatility and required strike on the day it is bought. If rates or volatility have risen since the original purchase, or the lender requires a tighter strike at extension, the premium rises.
Does a higher strike always save money?
Is a cap worth anything when the loan is paid off?
Yes, if time remains. The remaining caplets have market value, which can be large when the curve is above the strike. It should be counted in the disposition or refinancing analysis.
Is a rate cap calculator accurate enough to budget with?
For budgeting, yes, if the inputs match the loan and the curve and volatility are current. For buying, get competing quotes from qualifying counterparties.
Key takeaways
- A cap is a strip of caplets, and its cost is the sum of their values: intrinsic value from the forward curve plus time value from volatility.
- Strike against the forward curve drives most of the premium for strikes well below the curve; volatility drives most of it for strikes at or above the curve.
- Notional scales the premium; term adds caplets, and later caplets cost more when the curve rises.
- Replacement caps are priced on the day they are bought, often at a tighter strike, and escrows sized to that cost move with every review.
- Estimate intrinsic value yourself before taking quotes, and reprice every future replacement on the current curve.
Related reading
- Caps in your debt portfolio
- Hedge requirements, replacement caps and mark-to-market
- SOFR forward curve
- SOFR swap rates and fixed-rate debt
- Managing agency loans
- Interest rate cap and hedge mark-to-market in the glossary
The premium is the forward curve plus the price of uncertainty. LoanBoss keeps replacement cap costs live, so the next cap is a budget line and not a surprise.
Sources
- Freddie Mac Multifamily, Interest Rate Cap Options for Floating-Rate Cash Loans (May 2025)
- Freddie Mac Multifamily, Optigo Floating-Rate Loan term sheet (2026)
- Gupta and Subrahmanyam, An Examination of the Static and Dynamic Performance of Interest Rate Option Pricing Models in the Dollar Cap-Floor Markets (2001)
- Board of Governors of the Federal Reserve System, Heitfield and Park, Inferring Term Rates from SOFR Futures Prices, FEDS 2019-014 (2019)