Interest Rate Calculator

Find your effective interest rate.

What is the real interest rate you are paying on a loan? Our interest rate calculator finds the effective annual rate from your loan amount, monthly payment, and term, accounting for how compounding affects the true cost. It also helps you compare loan offers by showing the effective rate rather than just the advertised nominal rate. Understanding your real rate helps you spot expensive loans and negotiate better conditions. Free, instant, and completely private.

Calculate Interest Rate

​

How to Use the Interest Rate Calculator

Our free interest rate calculator determines the effective annual interest rate on any loan. Enter the loan amount, your desired monthly payment, and the loan term (in years). The calculator uses numerical approximation to find the exact interest rate that matches your payment.

Example Calculations

  • $10,000 loan, $200/month, 5 years: Effective annual interest rate = 7.42%. You can afford a $200 monthly payment on a $10,000 loan over 5 years at this rate.
  • $25,000 loan, $500/month, 5 years: Effective annual interest rate = 7.39%. Similar rate, larger loan amount scales proportionally.
  • $15,000 loan, $350/month, 4 years: Effective annual interest rate = 6.88%. A shorter term with a higher payment usually means a better rate.

Frequently Asked Questions

How do I calculate the interest rate on a loan?
Enter the loan amount, monthly payment, and loan term. The calculator uses iterative approximation to find your effective interest rate. This is useful when you know your desired payment but want to know the implied interest rate.

What is an effective interest rate?
The effective interest rate includes the effects of compounding, showing the true annual rate you earn or pay. It's higher than the nominal (stated) rate when compounding occurs more than once per year. This is the rate you should use for comparing loan offers.

What is the difference between APR and interest rate?
The interest rate is the cost of borrowing the principal. APR (Annual Percentage Rate) includes both the interest rate AND any additional fees (origination fees, closing costs), giving you a more complete picture of the true cost of borrowing.

How do I calculate the APR on a loan?
APR includes the interest rate plus any fees or costs associated with the loan. Our calculator helps you find the true cost by working backward from your desired monthly payment to determine the effective rate.

What is a nominal interest rate?
A nominal interest rate is the stated interest rate without adjusting for inflation or compounding. It's the rate you'll typically see advertised by lenders. The real interest rate (nominal minus inflation) gives you the true cost or return.

Also check our Loan Calculator, Mortgage Calculator, and other tools.