Interest Rate Calculator
Calculate interest rate from your own entered figures.
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Currency: Amounts are calculated in the currency you select; this site does not convert between currencies and does not use live exchange rates.
What this tool does
Calculate interest rate from your own entered figures. Solves for the nominal annual rate with monthly compounding. If the quoted payment includes financed fees or insurance, the solved rate is an effective (APR-like) rate, not the note rate.
How to use the Interest Rate Calculator
- Enter or select loan amount.
- Enter or select monthly payment.
- Enter or select term (months).
- Read the calculated result; change any measurement to compare alternatives.
Formula
invert the amortization formula by bisection: find the monthly rate whose level payment equals the entered payment, then annualize (rate × 12)
- amount
- Loan amount
- payment
- Monthly payment
- termMonths
- Term (months)
Solves for the nominal annual rate with monthly compounding. If the quoted payment includes financed fees or insurance, the solved rate is an effective (APR-like) rate, not the note rate.
Worked example
For interest rate calculator, the following measurements illustrate the exact method: Loan amount: 20000; Monthly payment: 386.66; Term (months): 60.
Inputs
- Loan amount$20000
- Monthly payment$386.66
- Term (months)60
Result
- Implied annual interest rate6%
- Total interest implied$3,199.60
- Total of all payments$23,199.60
Results explained
- Implied annual interest rate
- Implied annual interest rate from the formula above. Solves for the nominal annual rate with monthly compounding. If the quoted payment includes financed fees or insurance, the solved rate is an effective (APR-like) rate, not the note rate.
- Total interest implied
- Total interest implied from the formula above. Solves for the nominal annual rate with monthly compounding. If the quoted payment includes financed fees or insurance, the solved rate is an effective (APR-like) rate, not the note rate.
- Total of all payments
- Total of all payments from the formula above. Solves for the nominal annual rate with monthly compounding. If the quoted payment includes financed fees or insurance, the solved rate is an effective (APR-like) rate, not the note rate.
Frequently asked questions
invert the amortization formula by bisection: find the monthly rate whose level payment equals the entered payment, then annualize (rate × 12)
Solves for the nominal annual rate with monthly compounding. If the quoted payment includes financed fees or insurance, the solved rate is an effective (APR-like) rate, not the note rate.
No. All numbers are entered by you or come from the dated reference table shown on this page; calculations run locally.
This is an estimate, not financial, tax or legal advice. Verify the inputs and output with official sources and a qualified professional.
Check period consistency, currency, percentage inputs and the assumptions: Solves for the nominal annual rate with monthly compounding. If the quoted payment includes financed fees or insurance, the solved rate is an effective (APR-like) rate, not the note rate.