Interest Rate Calculator

Find the interest rate from a loan balance, term, and monthly payment.

Find the nominal annual rate implied by a fixed monthly payment.

Result

Annual interest rate5.7962%

How to use this calculator

Find the nominal annual rate implied by a fixed monthly payment. Enter amounts in the units shown, select the applicable options, and click Calculate. Use Reset to restore the starting values.

Calculation formula

Numerically solve P = A × (1 − (1+i)^−N) / i.

Assumptions and accuracy

Review timing, rates, fees and result notes when comparing scenarios. Future returns and rates are assumptions rather than guaranteed outcomes. Monetary display follows the currency’s precision; intermediate calculations retain additional digits.

Choose what to calculate

Loan interest rate calculator from monthly payment

Estimate the interest rate implied by a loan balance, payment and duration. Fees can make APR differ from this payment-implied rate.

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Understanding this calculation

Estimate a loan interest rate from principal, term and monthly payment. The solver finds a rate consistent with a fixed-installment repayment model.

Worked examples

Find the rate when payments equal principal

Illustrative inputs are specified in the steps below; the example link loads the complete settings. Unmentioned settings use the linked defaults.

Twelve monthly payments of 1,000 total 12,000, exactly the loan principal. With no fees in this model, the implied annual interest rate is zero.

Annual interest rate: 0%.

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Common questions

Can I find a loan's interest rate from its monthly payment?

Yes, when principal and term are also known and the fixed-payment assumptions fit the loan.

Why might the rate solver reject my payment?

For a nonnegative-rate repayment loan, installments must be sufficient to repay principal within the selected term. Check units and duration.

Scope and assumptions

This is an implied interest rate, not a fee-inclusive APR. A payment inconsistent with the model may have no supported solution.

Sources

Calculation notes checked October 20, 2026. Examples are mathematical checks under the stated assumptions.

Calculation methods and formulas

Interest Rate