Interest Rate Calculator

Find the interest rate given loan/savings amount, payment, and term

Loan Amount ($)

Monthly Payment ($)

Remaining Balance ($) — 0 if paid off

Term

About

Uses Newton-Raphson iteration to solve the time value of money equation for the interest rate. Nominal APR = monthly rate × 12. Effective APR = (1 + monthly rate)¹² − 1, accounting for compounding. Useful for comparing advertised rates.