Interest Rate Calculator
Calculate interest rate (APR) from loan amount, payment, and term.
Loan Terms
Calculated Rate
Annual Interest Rate (APR)
3.74%
About This Calculator
The Interest Rate Calculator helps you determine the interest rate (APR) when you know the loan amount, monthly payment, and loan term. This reverse calculation is useful for comparing loan offers or understanding the true cost of financing.
Sometimes lenders present loans with fixed payments without clearly stating the interest rate. This calculator allows you to calculate the implied interest rate based on your loan terms, helping you make informed financial decisions.
Formula & Calculation Method
Interest Rate Calculation:
Given: P (principal), PMT (payment), N (months)
Solve for R: PMT = P × R × (1+R)^N / [(1+R)^N - 1]
Where R = Monthly interest rate
Annual Rate = R × 12 × 100
Uses iterative method (Newton-Raphson) to solve for R
Since there's no direct formula to solve for interest rate, we use an iterative approximation method to find the rate that satisfies the loan payment equation. The calculator finds the monthly interest rate that makes the payment formula balance, then converts it to an annual rate.
How to Use This Calculator
- Enter Loan Amount: Input the total loan amount (principal).
- Enter Monthly Payment: Input the fixed monthly payment amount.
- Enter Loan Term: Input the loan duration in years.
- View Results: See the calculated interest rate (APR), total interest, and total payment.
- Compare: Use this to compare different loan offers and understand true costs.
Frequently Asked Questions
Why would I need to calculate the interest rate?
Sometimes lenders advertise loans with attractive monthly payments but don't clearly state the interest rate. This calculator helps you understand the true cost and compare different loan offers. It's also useful for analyzing existing loans.
Is this the same as APR?
The calculated rate is the annual percentage rate (APR) assuming no additional fees. True APR includes origination fees and other costs. This calculator shows the interest rate component of APR.
What if my loan has fees?
If your loan includes origination fees or other upfront costs, subtract those from the loan amount for more accurate rate calculation. Or add them to the total payment to see the effective rate.
How accurate is the calculated rate?
The calculator uses numerical methods to approximate the interest rate with high precision (within 0.01%). For most practical purposes, this provides accurate results for standard loan calculations.
Expert Reviewed
This calculator was reviewed by NumCalculators Editorial Team, Multi-disciplinary Expert Team