What it means
The word cap appears in many settings, from a cap on management fees to a cap on a company's liability in a contract, and in every case it means the same thing: a ceiling that cannot be exceeded. The most developed version is the interest rate cap, a derivative sold by banks to borrowers with floating-rate debt.
An interest rate cap is defined by four things: the notional amount it applies to, the strike rate that triggers a payment, the reference rate it is measured against, and the term over which it runs. If the reference rate settles above the strike on a reset date, the bank pays the difference on the notional for that period.
If it settles below, nothing happens and the buyer simply pays their normal floating interest. The buyer pays a one-off premium at the start, much like an insurance policy.
That premium rises with the length of the cap, the size of the notional and how close the strike is to current rates, because all three increase the chance of a payout. A cap set well above current rates is cheap but only helps in a severe move, while a cap set near current rates is expensive but starts paying quickly.
Caps are attractive because they are one-sided. A borrower who instead swaps into a fixed rate is locked in and will pay above market if rates fall, whereas a cap buyer keeps the benefit of falling rates and has already paid for the protection.
The cost of that flexibility is the premium, which is money spent whether or not the cap ever pays out. Lenders frequently make caps a condition of the loan rather than a choice.
Property and infrastructure lenders often require a borrower with floating-rate debt to buy a cap for the life of the facility, so that a rate spike cannot destroy the borrower's ability to service the loan. The cap is then assigned to the lender as part of the security package.
In practice
Real-world examples.
Example
A hotel group refinances with a $30 million floating-rate facility and the lender insists on a 6% cap for the full five-year term. The premium is $420,000, which the group treats as a financing cost and spreads across the life of the loan in its budgeting.
Example
A fund manager offers investors a cap on total expenses of 1.2% of assets, agreeing to absorb anything above that. When assets fall and fixed costs push the true ratio to 1.5%, the manager pays the difference and investors are charged only 1.2%.
Example
A software supplier negotiates a contractual liability cap equal to twelve months of fees. When an outage causes the customer a much larger loss, the supplier's exposure is limited to that agreed ceiling rather than the customer's full damages.
Formula
Calculation
Cap payout for a period = max(0, Reference rate - Strike rate) x Notional amount x (Days in period / 360)
A property developer has a $5,000,000 floating-rate loan and buys a cap with a 5% strike, settling quarterly, for an upfront premium of $60,000 over three years.
In one quarter the reference rate sets at 6.5%, which is 1.5% above the strike.
Rate difference = 6.5% - 5% = 1.5%.
Quarterly fraction = 90 / 360 = 0.25.
Payout = 1.5% x $5,000,000 x 0.25.
1.5% of $5,000,000 = $75,000.
$75,000 x 0.25 = $18,750.
The developer receives $18,750 for that quarter, which offsets the extra interest caused by the rate rising above 5%. In a quarter where the reference rate sets at 4.2%, the cap pays nothing and the developer simply enjoys the lower floating cost.Case study
Seen in the real world.
Brightfold Logistics is a fictional warehousing operator used for this illustrative example. It borrowed $25 million on a floating basis to fund three new distribution sites, with interest resetting quarterly. Its board was comfortable at the prevailing 4% rate but had modelled that anything above 7% would consume the entire operating margin of the new sites.
Rather than swapping into a fixed rate of 5.4%, which would have cost an extra 1.4% a year from day one, the team bought a four-year cap with a 6.5% strike for a premium of $350,000. That premium was roughly what one year of the swap's extra cost would have been, and it left the company exposed to rates only within a band it could absorb.
Rates then rose to 8% over the following two years. In this illustrative scenario the cap paid out roughly $375,000 a year while rates sat 1.5% above the strike, more than recovering the premium, and Brightfold's interest bill was held at the equivalent of 6.5%. Had rates instead fallen to 2%, the company would have lost the premium but paid far less interest than a fixed-rate borrower.
Watch out
Common mistakes.
- Thinking a cap fixes your interest cost. It only sets a maximum; below the strike you still pay the floating rate, which is the whole point of buying one.
- Judging a cap purely on the premium. A cheap cap usually has a strike so high that it only helps in an extreme move, which may not be the risk you were trying to cover.
- Forgetting that the cap's reset dates and reference rate must match the loan's. A mismatch leaves gaps where the loan reprices but the cap does not, so the protection is incomplete.
Questions
People also ask.
Is a cap the same as a collar?
No, a collar combines a bought cap with a sold floor, which reduces or removes the premium but also gives up the benefit of rates falling below the floor.
Who pays the premium on an interest rate cap?
The borrower buying the protection pays it upfront to the bank selling the cap, though some lenders will finance it within the loan.
What happens to a cap if the loan is repaid early?
The cap is a separate contract and continues unless it is terminated or sold, and it usually has a market value that can be realised.
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