Financial tools

Implied Interest Rate Calculator

Enter the amount financed, number of equal monthly installments, and installment value to estimate the implied monthly interest rate, effective annual rate, total repayment, and interest cost.

Enter the payment plan details

Enter the amount financed, number of equal monthly installments, and value of each installment. The total amount is treated as the principal borrowed, with payments made at the end of each month.

How this implied interest rate calculator works

This calculator estimates the interest rate built into a fixed installment plan. Provide the total amount financed, how many equal installments are due, and the amount of each installment. The result helps you compare payment offers by showing both the monthly rate and the effective annual rate.

Monthly and effective annual interest rates

The monthly rate is solved from the present value of the installments and the amount financed. The nominal annual rate is the monthly rate multiplied by 12. The effective annual rate compounds the monthly rate for 12 months: (1 + monthly rate)¹² − 1.

Estimate only

The calculation assumes equal payments at the end of each month and a constant rate. Fees, taxes, insurance, payment timing, and lender-specific rounding are not included. Compare this estimate with the lender’s full contract and payment schedule.