Interest Rate Cap Calculator

Calculate monthly payments on floating-rate loans with interest rate caps and floors. Compare uncapped vs. capped payments, total savings from cap protection, and payment curves across rate scenarios. For ARM mortgages, SOFR-linked loans, and commercial real estate debt.

Loan Principal ($)

Index Rate (e.g., SOFR) (%)

Spread Above Index (%)

Rate Cap (Maximum) (%)

Rate Floor (Minimum) (%)

Loan Term (years)

yrs

mos

Current Monthly Payment

$9,960.00

Payment at Rate Cap

$10,138.00

Payment at Rate Floor

$8,764.00

Monthly Savings from Cap

$0.00

Total Savings Over Term

$0.00

Cap Status

Out of the Money

What is Interest Rate Cap Calculator?

An interest rate cap is a financial derivative that protects floating-rate borrowers from rate spikes by setting a contractual ceiling on the interest they pay. It is widely used in commercial real estate (CRE) financing, adjustable-rate mortgages (ARMs), and corporate debt. When the reference rate — today typically SOFR (Secured Overnight Financing Rate) — rises above the cap strike, the cap seller pays the borrower the difference, effectively capping the borrower's interest cost. Borrowers purchase this protection upfront by paying a cap premium. A rate floor (the lower boundary) may also apply, either as lender protection or as part of a collar structure where the floor premium offsets the cap cost. This calculator lets you model the full payment landscape: what you pay today at the current rate, the maximum you'll ever pay at the cap, the minimum at the floor, and your total dollar savings from cap protection over the life of the loan.

Formula

Monthly payment = P × r × (1 + r)^n ÷ ((1 + r)^n − 1)

where P = principal, r = monthly rate (annual ÷ 12), n = term in months

Effective rate = min(max(index + spread, floor), cap)

Monthly savings from cap = payment at uncapped rate − payment at capped rate

Total term savings = monthly savings × number of monthly payments

How to Calculate

Enter your loan principal amount
Enter the current index rate (e.g., SOFR is approximately 5.25% as of 2024)
Enter your spread above the index (e.g., 200 basis points = 2.00%)
Enter your rate cap — the maximum interest rate you are protected against
Enter your rate floor — the minimum rate (enter 0 if no floor applies)
Enter the loan term in years
Review current, capped, and floored payments and total savings
Analyze the payment curve chart to understand your exposure across all rate scenarios

Example

A $5,000,000 commercial real estate loan at SOFR (5.25%) + 200 bps spread = 7.25% current rate. Cap at 9.00%, floor at 2.00%, 5-year term. Current monthly payment: $99,400. Payment at cap (9%): $103,800. Payment at floor (2%): $88,200. Monthly savings from cap vs. uncapped at 9%: $0 (cap not yet in the money). If SOFR rises to 7.5% (total rate 9.5%), the cap saves $4,400/month — $264,000 over 60 months.

Key Benefits

Instantly compare capped, uncapped, and floored payment scenarios
Calculate total dollar savings from cap protection over the loan term
Visualize your full payment curve across all rate scenarios between floor and cap
Essential modeling tool for CRE borrowers, ARM holders, and treasury professionals
All calculations are local — no financial data is shared or stored

Common Mistakes to Avoid

Assuming the cap eliminates all rate risk — the cap only protects above the strike rate; you still face rate increases up to the cap level
Ignoring the cap premium cost when calculating total loan economics — a $150,000 cap premium is a real cost that should be amortized
Comparing the floor rate payment to a fixed-rate loan without accounting for the potential savings when rates fall below the floor

Pro Tips

Model the worst-case scenario (rates rise to the cap) to confirm the capped payment is still serviceable with your cash flow
When structuring a collar (cap + floor), choose a floor rate that covers your debt service minimum while reducing cap premium cost
Compare the rate cap premium against the total savings at the cap rate over your expected hold period to assess value

Key Terms Explained

Rate Cap: A contractual ceiling on a floating interest rate — you never pay above this rate regardless of market moves
SOFR: Secured Overnight Financing Rate — the US benchmark rate replacing LIBOR, used in most modern floating-rate loans
Spread: The fixed margin above the index rate — your all-in rate is index + spread (unless capped or floored)
In the Money: When the current floating rate exceeds the cap rate — the cap is actively saving you money
Floor Rate: The minimum interest rate on the loan — protects the lender from very low rates in a collar structure

Common Use Cases

Modeling payment scenarios for commercial real estate floating-rate debt with rate caps
Comparing the cost-benefit of purchasing a rate cap vs. accepting rate risk on an ARM
Analyzing the impact of SOFR rate changes on loan payments with embedded cap protection
Treasury teams modeling interest rate risk on variable-rate corporate debt
Lenders and brokers structuring floating-rate loan products with cap and floor provisions

Frequently Asked Questions

What is an interest rate cap?

An interest rate cap is a financial derivative that sets a ceiling on a floating interest rate. If the reference rate (e.g., SOFR) rises above the cap rate, the cap holder pays no more than the capped rate — the seller of the cap absorbs the excess. Borrowers pay an upfront premium for this protection.

What is the difference between a rate cap and a rate collar?

A rate cap sets only a ceiling (maximum rate). A rate collar combines a cap (maximum) with a floor (minimum), creating a band. The floor limits how low your rate can fall. Collars reduce the upfront premium because the floor provides partial funding for the cap.

When is a rate cap "in the money"?

A rate cap is in the money when the current floating rate (index rate + spread) exceeds the cap rate. You are then actively protected — paying the capped rate while the seller covers the difference. When the current rate is below the cap, the cap is out of the money — protection you hold but are not yet using.

What is a SOFR-based floating rate loan?

SOFR (Secured Overnight Financing Rate) is the benchmark rate that replaced LIBOR in 2023 for most US floating-rate debt. A SOFR loan charges interest at SOFR plus a fixed spread — the all-in rate changes with market conditions. Rate caps on SOFR loans are now standard in many commercial real estate transactions.

How much does an interest rate cap cost?

Rate cap premiums depend on the strike rate (cap), loan term, current rate levels, and market volatility. In high-rate, high-volatility periods, caps are more expensive. Typical premiums range from 0.5% to 3%+ of the notional loan amount for a 2–5 year cap term.