Calculate your exact monthly payment, total interest paid, and full repayment schedule for any personal, auto, or student loan. Enter three numbers and see everything instantly — including a complete month-by-month amortization breakdown.
This calculator uses the standard amortization formula to compute your exact monthly payment. Three inputs are all you need — change any value and results update instantly.
To compare loan options, change one input at a time. Try reducing the rate by 0.5% or shortening the term by one year — the calculator shows you the exact dollar impact immediately.
The amortization formula produces a fixed monthly payment where each payment covers that month's interest first, then reduces the principal. Here is exactly how your $615.50 payment was derived from the numbers above.
Three common loan scenarios calculated with exact numbers. Use these as a reference point, then adjust the calculator above to match your own situation.
Every fixed-rate installment loan — personal, auto, or student — uses the same amortization formula. The formula produces a constant monthly payment that covers that month's interest first, then reduces the outstanding principal. Because interest is calculated on the remaining balance, early payments are mostly interest and later payments are mostly principal. This is why paying even a modest extra amount in year one saves far more than the same amount in year four.
Where M is the monthly payment, P is the principal, r is the monthly interest rate (annual ÷ 12 ÷ 100), and n is the total number of payments (years × 12).
Extending your loan term lowers monthly payments but dramatically raises total interest paid. The table below shows the exact trade-off on a $20,000 loan at 7.5%.
| Term | Monthly payment | Total interest | Total paid |
|---|---|---|---|
| 2 years | $903 | $665 | $21,665 |
| 3 years | $622 | $2,391 | $22,391 |
| 5 years | $401 | $4,046 | $24,046 |
| 7 years | $307 | $5,791 | $25,791 |
Going from 2 years to 7 years saves $596 per month — but adds $5,126 in total interest, roughly 25% of the original loan. The strategic question is whether that monthly saving can be deployed elsewhere at a higher return than 7.5%. For most borrowers, the shorter term wins on total net wealth.
When a lender quotes you a rate, they present two figures: the interest rate (the base charge applied to your balance) and the APR (Annual Percentage Rate, which folds in origination fees, discount points, and other financing costs). By law under TILA, lenders must disclose the APR on all consumer loans — making it the only standardized basis for comparison across lenders.
If the APR is 0.1–0.3% above the stated rate, fees are modest. If the gap is 0.5% or more, origination costs are significant — negotiate, shop competing offers, or ask the lender to reduce fees in exchange for a marginally higher rate.
These four approaches have the highest impact on reducing total loan cost — ranked by the typical dollar savings they produce.
For mortgage-specific analysis including PMI, PITI, and LTV calculations, use the mortgage calculator. For a complete payment-by-payment breakdown, see the amortization calculator.