The three inputs that decide your payment
Every loan calculator boils down to three numbers:
- Principal — the amount you're borrowing.
- Interest rate — the annual cost of borrowing, expressed as a percentage.
- Term — how long you have to repay it, usually in months or years.
Change any one of these and your monthly payment shifts — but not always in the direction people expect. A longer term lowers the monthly payment but increases the total interest paid over the life of the loan.
Rate vs. APR — they're not the same thing
The interest rate is just the cost of borrowing the principal. APR (Annual Percentage Rate) folds in additional fees — origination fees, processing charges — into a single annualized figure, which makes it a better number for comparing loans from different lenders. Two loans can advertise the same interest rate and have meaningfully different APRs.
How amortization actually works
Early in a loan, a larger share of each payment goes toward interest; later payments shift toward paying down principal. This is why an extra payment made early in a loan's term saves more total interest than the same extra payment made near the end — it reduces the principal balance that all future interest is calculated on.
How to use the calculator
Enter principal, rate and term
Use the exact APR from your loan offer, not just the headline rate.
Read the monthly payment
The Loan Calculator also shows total interest paid over the full term.
Compare scenarios
Try different terms side by side to see the real trade-off between monthly payment and total cost.
If you can afford a shorter term's higher payment, it almost always costs less in total interest than a longer term — even at the same rate.
Run the numbers on your loan
Free, instant, and shows total interest — not just the monthly payment.