Interest Rate Calculator
Know the amount, the payment and the duration? Find the interest rate you're really paying.
—Annual interest rate (nominal)
—Effective annual rate
—Monthly rate
—Total interest
—Total repaid
● Calculations run in your browser. Your numbers are never sent anywhere.
How it works
There's no direct formula for the rate, so the tool searches for the monthly rate r that makes the payment formula match your numbers (by bisection, to 10 decimal places), then annualizes it: the nominal rate is r × 12 and the effective annual rate (1 + r)12 − 1 includes compounding. Fees paid upfront aren't included — subtract them from the amount borrowed to approximate the APR.