How to use this tool
Enter the principal, equal monthly payment and total number of payments.
Read the inferred nominal annual rate. It excludes fees and supports nonnegative rates only.
Find r such that payment × [1 − (1+r)^−n] / r = principal
Worked example
6% · nominal annual rate
Fixed example using the settings below. Monetary examples use USD; dates and times use their stated reference values. This example stays unchanged when you edit your calculation.
Example inputs
- Principal: 20000
- Monthly payment: 386.6560306
- Number of payments: 60
Method illustration: 20,000 repaid with 60 payments near 386.66 implies about 6% nominal annually.
Assumptions and limits
- Equal monthly payments at period end; no upfront fee or balloon. This is not a fee-inclusive APR.
- Solves nonnegative rates up to 100% nominal annually. Unsupported negative rates are reported.
Method reference: Nominal monthly-rate convention
Check or report a result
Check the units, selected calculation and assumptions first. Compare the fixed example above with your inputs to identify what changed.
Report a calculation issue with the page address, hypothetical inputs, result displayed and result expected. Do not include passwords, bank details or other private information.