How do interest rate caps, floors, and collars work? Can someone explain with a practical loan example?

Interest rate caps, floors, and collars are essential hedging instruments and a staple of CFA Level II Derivatives. Let's build the intuition from a real scenario.

The Setup: A Floating-Rate Borrower

Dunbar Energy borrows $50M at a floating rate of SOFR + 200bp, with quarterly resets over 2 years. They're worried that if SOFR rises above 5%, their interest cost becomes unsustainable.

Interest Rate Cap

Dunbar buys a 5% cap on 3-month SOFR for a premium of $180,000.

A cap is a series of caplets — one for each reset period. Each caplet is essentially a call option on the interest rate.

Caplet Payoff (each quarter):

Payoff = max(SOFR − Cap Rate, 0) × Notional × (days/360)

If SOFR resets at 6.2% in Q3:

• Payoff = max(6.2% − 5.0%, 0) × $50M × (90/360)
• Payoff = 1.2% × $50M × 0.25 = $150,000

This payment offsets the extra borrowing cost above 5%.

Interest Rate Floor

A floor works in reverse — it benefits if rates fall below a threshold. It's a series of floorlets, each a put option on the interest rate.

A lender (or investor holding floating-rate notes) might buy a 3% floor to guarantee minimum interest income.

Collar = Cap + Floor

Dunbar can reduce the cap premium by simultaneously selling a 3% floor. This creates a collar — they're protected above 5% but give up any benefit if SOFR drops below 3%.

Net Result for the Collar:

• Dunbar's borrowing cost is bounded between 5.0% (floor + spread) and 7.0% (cap + spread)
• The floor premium received partially or fully offsets the cap premium paid
• If the premiums are equal, it's a zero-cost collar

Valuation Insight:

Each caplet and floorlet can be priced using the Black model (a variant of Black-Scholes for interest rate options). The total cap/floor value is the sum of individual caplet/floorlet values.

CFA Exam Tip: Questions often ask you to calculate the net interest payment under a collar given a specific SOFR reset rate. Remember to add the spread separately — the cap/floor only covers the reference rate.

For more derivatives practice, visit our CFA Level II question bank.