Is an interest rate cap better than fixing the rate?

Neither is better in general. A fixed rate or swap gives certainty and costs nothing up front, but gives up any fall in rates and can leave a break cost. A cap leaves the interest bill floating below the strike and costs a premium that is gone whether or not rates rise. The choice depends on how much the business can absorb, how long the debt will stay in place and what the two are quoted at on the day.

How much does an interest rate cap cost?

It depends on the strike, the term, the notional and the market's expectations and volatility for interest rates at the time. The closer the strike is to where rates are expected to go, and the longer the term, the higher the premium. There is no standard price, and the same cap can cost several times more in a volatile market. The figure in this page's example is constructed for the example and is not a guide to current pricing.

What happens to a cap if I repay the loan early?

The cap is a separate contract and does not end when the loan does. The holder can usually keep it, or sell it back to the provider for whatever it is then worth, which may be little or nothing if rates are well below the strike. Unlike a swap, a cap bought with its premium fully paid does not create a further amount for the holder to pay on exit. Any unpaid instalments of a deferred premium would still be owed.

Does a cap limit my margin?

No. A cap applies to the base rate only. The margin is the lender's price for the credit risk and sits on top of whatever the base rate does, so the most a capped borrower pays is the strike plus the margin, before the premium. If the margin steps up under a ratchet because leverage has risen, the all-in rate rises with it, and the cap does nothing about that.

// WORKED EXAMPLETHE ARITHMETIC A DECISION RESTS ON

Interest Rate Cap: a Worked Example

A ceiling on the base rate, bought with a premium.

BY MICHAEL SHANG · SIXTEEN YEARS IN COMMERCIAL BANKING · UPDATED 2026-11-09 · 6 MIN READ

// THE SHORT ANSWER

An interest rate cap answers a narrower question than a fixed rate: what is the worst this loan can cost? The borrower pays a premium and receives a payment in any period the base rate sets above an agreed strike, so its interest bill stops rising at that level while it keeps the benefit of lower rates. On a US$20m loan with a 5.00 strike and a 2.25 margin, the ceiling is 7.25 before the premium. A lender can test debt service at that figure, which is why the strike and the premium, not the word cap, decide what the protection is worth.

BASIS Practitioner judgment from sixteen years in commercial banking, set out in How Bankers Think (Highbank Press, 2026). Every borrower on this site is a composite constructed for teaching, not a client. The market is mid-market commercial lending as practised in New Zealand and Australia; where a convention differs elsewhere, the page says so.

// MAKE THE CALL

Issue 02 — Aoraki Trade Exports. Paid in USD, costs in NZD, asking for a NZ$6m multi-currency facility. The MD won't say which currencies. Your call first, then the senior banker's.

Read the file →

PART OF Foreign Exchange Facilities

// 01 — WHAT THE CAP DOES AND WHAT THE LENDER SEES

A floating-rate loan charges a base rate plus a margin, and the base rate resets each period: a bank bill rate (BKBM or BBSY) in New Zealand and Australia, and commonly SONIA or the Bank of England's Bank Rate in the UK. A cap is a separate contract from the loan. At each reset, if the base rate is above the strike, the cap's seller pays the borrower the difference on the notional amount for that period. If the rate is at or below the strike, nothing is paid and the borrower simply pays the lower rate.

A lender cares because a floating-rate borrower's interest is the one large cost that can rise with nothing in the business having changed. A cap puts a known limit on that cost for the life of the contract. Once the premium is paid, the borrower owes nothing further under it, so it does not create the credit exposure a swap can. The risk runs the other way: the borrower is relying on the seller to pay.

// 02 — HOW IT IS BUILT AND PRICED

Payment each period = notional × (base rate − strike) × fraction of year

(nothing if the base rate is at or below the strike)

Ceiling on the loan = strike + margin

Effective ceiling = strike + margin + premium, spread over the term

A cap is a series of options, one for each reset date, called caplets. Its premium is driven by how far the strike sits above where rates are expected to go, the term, the notional and how volatile rates are expected to be: a lower strike or a longer term costs more. The premium is often paid at the start, but the UK regulator's description of these products notes that it can be an upfront fee, an ongoing premium or both. Where it is paid over time, the unpaid part is a debt to the seller.

The notional should follow the loan. On an amortising loan a cap with a flat notional protects more than is owed in later years, the over-hedging problem in a mild form. The reset dates and the rate index should match too: a loan on a 30-day rate with a cap on a 90-day rate leaves a gap.

// 03 — THE EXAMPLE

A group of childcare centres, constructed for this page like every figure in it, borrows US$20m for three years at the base rate plus 2.25. The base rate is 3.75 today. Its bank quotes a three-year cap at a 5.00 strike for a premium of 1.20% of the notional, or a three-year swap at 4.40. Those prices are the example's and depend on the market on the day.

Premium: 20,000,000 × 1.20% = US$240,000

Per year: 240,000 ÷ 3 = 80,000 = 0.40% on US$20m

Base rate With the cap With the swap

3.00 3.00 + 2.25 + 0.40 = 5.65 4.40 + 2.25 = 6.65

4.00 4.00 + 2.25 + 0.40 = 6.65 4.40 + 2.25 = 6.65

5.00 5.00 + 2.25 + 0.40 = 7.65 4.40 + 2.25 = 6.65

6.50 5.00 + 2.25 + 0.40 = 7.65 4.40 + 2.25 = 6.65

Spreading the premium evenly ignores the time value of money, which is close enough for this comparison. The two cost the same at a base rate of 4.00. Below that the cap is cheaper and above it the swap is, by as much as a full point. In a quarter when the base rate is 6.50, the cap pays:

20,000,000 × (6.50% − 5.00%) × ¼ = US$75,000 for the quarter

Now the lender's view. The group's EBITDA is US$3.6m. If the base rate went to 7.00 with no protection, interest would be 9.25% of US$20m, or US$1.85m, and interest cover 1.95 times. With the cap, interest net of the payment is 7.25%, or US$1.45m, and cover 2.48 times, before counting the premium already paid. The stress result depends on the strike, and a higher strike would be cheaper and leave less.

// 04 — HOW IT DIFFERS FROM A SWAP AND A COLLAR

A swap fixes the base rate and needs no premium at the outset, but it can leave the borrower owing the bank money, and that value becomes a break cost if the swap is closed early, as it commonly is when the loan is repaid. A cap costs more visibly and less dangerously. A business that needs certainty, because its prices are fixed or its margin is thin, usually compares the swap first. One that can absorb a moderate rise and needs protection only against a severe one looks at a cap.

A collar buys a cap and sells a floor to pay for it, so the borrower gives up part of the benefit of lower rates and can owe money when rates fall below the floor. Do not confuse it with an interest rate floor written into the loan itself, which protects the lender's return on the base rate.

DEFINED IN ONE PARAGRAPH → · A SWAP, FROM THE BORROWER'S SIDE → · INTEREST RATE COLLAR →

// 05 — WHERE IT DECIDES A FILE

Where a facility requires part of the debt to be hedged, the agreement says whether a cap counts, and it may set conditions on the strike or on who may sell it. The hedge ratio a lender records is only as good as that wording. A cap with a strike far above current rates may satisfy the document and still leave the interest bill exposed to a large rise before it pays anything.

An upfront premium is also a use of funds. It leaves the business on day one and belongs in the sources and uses. If the cap is bought from a party other than the lender, the lender will want to know who owes the payments and may ask for rights over the proceeds. And in the UK, the regulator's review of hedging sold to small businesses treated caps as the least complex category, reviewing a sale only where a non-sophisticated customer complained.

HEDGE RATIO → · INTEREST COVER → · FINANCIAL MANAGEMENT, READ BY A LENDER →

// SOURCES

The documents the statements on this page rest on. Each was opened and checked when cited.

Financial Conduct Authority, Interest rate hedging products: background to the review — Describes a cap as a contract separate from the loan, with an upfront fee, an ongoing premium or both, a lower agreed rate costing more, and a payment by the bank only when base rates exceed the agreed rate — sections 01 and 02.
Financial Conduct Authority, Interest rate hedging products: the review — Places caps in category C, described as the least complex, reviewed only if a customer complains — section 05.
Bank of England, SONIA interest rate benchmark — The Bank of England administers SONIA, an overnight sterling rate based on actual transactions — section 01.

// QUESTIONS PEOPLE ASK

Is an interest rate cap better than fixing the rate?: Neither is better in general. A fixed rate or swap gives certainty and costs nothing up front, but gives up any fall in rates and can leave a break cost. A cap leaves the interest bill floating below the strike and costs a premium that is gone whether or not rates rise. The choice depends on how much the business can absorb, how long the debt will stay in place and what the two are quoted at on the day.
How much does an interest rate cap cost?: It depends on the strike, the term, the notional and the market's expectations and volatility for interest rates at the time. The closer the strike is to where rates are expected to go, and the longer the term, the higher the premium. There is no standard price, and the same cap can cost several times more in a volatile market. The figure in this page's example is constructed for the example and is not a guide to current pricing.
What happens to a cap if I repay the loan early?: The cap is a separate contract and does not end when the loan does. The holder can usually keep it, or sell it back to the provider for whatever it is then worth, which may be little or nothing if rates are well below the strike. Unlike a swap, a cap bought with its premium fully paid does not create a further amount for the holder to pay on exit. Any unpaid instalments of a deferred premium would still be owed.
Does a cap limit my margin?: No. A cap applies to the base rate only. The margin is the lender's price for the credit risk and sits on top of whatever the base rate does, so the most a capped borrower pays is the strike plus the margin, before the premium. If the margin steps up under a ratchet because leverage has risen, the all-in rate rises with it, and the cap does nothing about that.

// NEXT TO IT

// ON WHOSE DESK

The seats that read this term in an ordinary week. Each page says what the seat is for, who arrives in it, and the shape of the round it runs.

Markets salespersonSells the bank's markets products — foreign exchange, interest rate hedging, commodities — to corporate and institutional clients.
Treasury analystFunds the bank and manages the interest rate and liquidity risk created by its own balance sheet.
Corporate coverage bankerOwns the bank's relationship with a large corporate or institutional client and orchestrates everything the bank sells into it.

THE IN-TRAY · ONE MINUTE

Make the call on one file.

A short file on the ground this page covers. Every option opens with how far it sits from a senior banker’s read.

THE FIRST QUESTION · THE LOAN · HEDGES

A borrower has a US$10m floating-rate loan and an interest rate swap fixing the rate on US$15m.

What do you ask first?

6 MORE ON THE LOAN · HEDGES →WHERE DO YOU READ FROM? THE PLACEMENT →

THE READING ROOMIN ONE PARAGRAPHInterest rate cap What is an interest rate cap, and how is it different from a swap?