Understanding the interest rate calculator
Sometimes you know the loan amount, the monthly payment, and the term, but not the interest rate a common situation with dealer financing or informal loans where the rate is buried. There's no simple algebraic formula to isolate the rate, so this calculator solves for it numerically, finding the rate that makes the payment amortize the balance exactly.
Knowing the implied rate turns an opaque offer into something you can compare. A "$400 a month for five years" pitch on a $20,000 loan sounds harmless until you see it's a specific APR and once you have that number, you can shop it against other lenders or decide whether paying cash makes more sense.
Results are estimates for education only and are not financial advice.