= FastCalcs
Please double-check important results before using them for decisions.

Finance

Interest Rate Calculator

Estimate the annual interest rate from loan amount, payment, and a term entered in years or months.

Interest Rate inputs

Back into the implied APR-like rate when you know the payment and loan details.

Estimated annual rate 0
Total paid 0
Total interest 0

This calculator is for general information only and is not financial, tax, lending, investment, or legal advice. Actual loan terms, rates, fees, taxes, and qualification rules can vary by lender, country, and personal situation.

Formula

The calculator solves the standard amortization formula for the monthly interest rate, then annualizes it.

Example

A $25,000 loan paid at $500 per month for 5 years implies an annual rate near 7.4%.

Result notes

  • Results are estimates based on the values you enter.
  • Calculators with schedules show how values change over time.
  • For financial, health, or construction decisions, compare these estimates with professional advice when needed.

Frequently asked questions

Is this exactly APR?

No. APR can include fees and lender-specific rules. This estimates the rate implied by payment math.

What if the payment is too low?

If the payment cannot amortize the loan, the calculator returns a warning.

Why solve by iteration?

There is no simple closed-form solution for the rate in the amortization formula.

Related calculators