Interest Rate Calculator
Find the real interest rate of a loan from the amount, payment and term.
How to use Interest Rate Calculator
- Enter the amount you borrow (after any down payment).
- Enter the monthly payment and how many payments there are.
- Read the yearly rate those payments imply, the effective annual rate and the total interest.
How it works
A loan’s payment formula, M = P × r ÷ (1 − (1 + r)⁻ⁿ), cannot be rearranged to give the rate r directly. The tool finds it numerically: it tries monthly rates by bisection until the present value of the payments equals the amount borrowed, to far more decimal places than are shown.
The yearly rate shown is the monthly rate × 12, the way loan rates are normally quoted. The effective annual rate includes monthly compounding: (1 + r)¹² − 1. A lender’s APR also spreads compulsory fees over the loan, so if you paid fees the APR will be higher than the rate shown here; to approximate it, subtract the fees from the amount borrowed.
Example
Borrow 20,000 and repay 400 a month for 60 months: you pay 24,000 in total, 4,000 of it interest. The rate that makes this work is 7.42% a year (7.68% effective).
Frequently asked questions
How do I find the interest rate on my loan?
Enter the amount borrowed, your monthly payment and the number of payments. The calculator finds the only rate at which those payments repay that amount.
Why is this different from dividing interest by the amount?
4,000 interest on 20,000 over 5 years looks like 4% a year, but you owe less each month as you repay, so the true rate on what you still owe is much higher: 7.42% in this example.
Is this the APR?
It is the rate implied by the payments. APR also counts fees. If you paid a fee, subtract it from the amount borrowed and the result will be close to the APR.
What is a good interest rate?
It depends on the kind of loan, your credit and the market at the time. Compare offers from several lenders on the same day.
Limitations
- Equal monthly payments only.
- Fees are not included unless you subtract them from the amount.
- Rates above 1,200% a year are not solved.
Last reviewed November 9, 2026. How we build and test tools.