How is the rate found?

There is no closed-form solution, so the calculator solves numerically (bisection) for the rate that makes the payment match the loan over the term.

Interest Rate Calculator

Back-solve the annual interest rate of a loan from its amount, monthly payment, and term — useful when a lender quotes a payment but not the rate.

How is the rate found?: There is no closed-form solution, so the calculator solves numerically (bisection) for the rate that makes the payment match the loan over the term.

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