How to use the Interest Rate Calculator
This calculator finds the interest rate hidden in a loan quote, given the amount, the monthly payment and the term.
Open the Interest Rate Calculator →
What you need to enter
- Loan amount ($)
- Monthly payment ($)
- Loan term (years)
The formula
It solves payment = P × r ÷ (1 − (1 + r)^−n) for r by repeated searching, then multiplies by 12 for the annual rate.
Worked example
Using the default values in the calculator:
- Loan amount ($): 20000
- Monthly payment ($): 400
- Loan term (years): 5
| Interest rate (APR) | 7.42% |
| Total interest | $4,000.00 |
Tips for better results
- Use it to check dealer or store financing that does not state a rate.
- Compare the rate with other offers before accepting.
Common mistakes to avoid
- Forgetting fees, which raise the true cost beyond this rate.
- Mixing up monthly and yearly rates.
Please note: Calculators and guides give general estimates, not financial, tax or investment advice. Real offers depend on your lender, location and personal situation. See our Disclaimer.