Interest Rate Calculator
Estimate the nominal annual rate implied by a fixed loan principal, term and monthly payment.
FREE ONLINE CALCULATOR
Interest Rate Calculator
Change the settings below to calculate your result. You can check the assumptions further down this page.
Find the monthly rate for which the standard amortizing payment equals the stated payment.
How to use this interest rate calculator
This tool numerically solves the loan payment equation. It assumes equally spaced monthly payments and no extra charges.
Formula and calculation method
Find the monthly rate for which the standard amortizing payment equals the stated payment.
Worked example
Two loans with the same balance and term can have different monthly payments because the interest rates differ.
Understanding the result
The solver estimates an interest rate from three pieces of information: what was borrowed, how long it is repaid and the payment. It cannot recover lender fees or the exact contract APR because those details are not present in the calculation.
When to use this calculator
Check that you enter the amount actually financed rather than the original purchase price. If the payment is smaller than the principal divided by the number of payments, there is no nonnegative loan rate that fits those inputs.
What the results do not include
An inferred nominal rate is not necessarily the lender’s disclosed APR, which may include fees.
Frequently asked questions
Why is there no solution?
The proposed payment may be less than the no-interest amount needed to repay the principal.
Does this calculate APR including fees?
No. It calculates the rate implied by principal and regular payments only.
For education and estimates only. Check any contractual, tax, banking or employment terms that apply to your situation. The calculations are not financial advice or guaranteed returns.