The Interest Rate Calculator determines real interest rates on loans with fixed terms and monthly payments. For example, it can calculate interest rates in situations where car dealers only provide monthly payment information and total price without including the actual rate on the car loan. To calculate the interest on investments instead, use the Interest Calculator, or use the Compound Interest Calculator to understand the difference between different interest rates.
When dealerships, lenders, or sellers quote a monthly payment without disclosing the actual interest rate, this reverse solver uses exact numerical root-finding (Newton-Raphson) to uncover the exact Annual Percentage Rate (APR).
Tracking Remaining Balance (Blue), Cumulative Interest (Green), and Cumulative Payments (Maroon).
Principal vs. Total Interest share of total payments.
Detailed schedule of principal reduction, interest charges, and remaining balances.
| Year | Beginning Balance | Total Payments | Principal | Interest | Cumulative Interest | Ending Balance |
|---|---|---|---|---|---|---|
| Year 1 | $32,000.00 | $11,520.00 | +$10,132.33 | +$1,387.67 | $1,387.67 | $21,867.67 |
| Year 2 | $21,867.67 | $11,520.00 | +$10,657.59 | +$862.41 | $2,250.08 | $11,210.08 |
| Year 3 | $11,210.08 | $11,520.00 | +$11,210.08 | +$309.92 | $2,560.00 | $0.00 |