Loan Calculator
What will this loan really cost? Monthly payment, total interest, a visual amortization schedule — and a prepayment lab that shows exactly what extra payments save you. Free, private, no signup.
Your loan
See how much time and interest an extra payment saves.
Monthly payment
-
Total interest-
Total cost of loan-
Payoff date-
Prepayment lab
With extra payment-
Time saved-
Interest saved-
New payoff date-
Balance over time
■ Remaining balance ■ With extra payments
Year-by-year amortization
| Year | Principal | Interest | Balance |
|---|
How loan amortization actually works
Your monthly payment never changes — but what is inside it does. Every month the lender takes interest on the remaining balance first, and whatever is left reduces the principal. Early on, the balance is huge, so most of your payment is interest. Late in the loan, it is almost all principal.
- Extra payments attack principal directly. Because interest is charged on the balance, every extra dollar early in the loan prevents interest from compounding on it for years. That is why small extra payments save disproportionate interest.
- Rate beats term for total cost. A 1% lower rate usually saves more than shaving a few years off the term — run both scenarios above.
- The 15 vs 30 year trade-off. A 15-year loan at the same rate roughly halves total interest but raises the payment 40-50%. Only take the payment you can make in a bad month, not a good one.
Fixed vs adjustable rates
This calculator assumes a fixed rate for the whole term. Adjustable-rate mortgages (ARMs) reset periodically — if yours does, re-run the numbers with the new rate and remaining balance at each reset.
FAQs
How is the monthly payment calculated?
With the standard amortization formula: payment = P × i(1+i)n / ((1+i)n − 1), where P is the loan amount, i the monthly rate and n the number of payments.
Do extra payments reduce my payment or my term?
This calculator assumes the payment stays the same and the term shrinks, which saves the maximum interest. Some lenders recast the loan (lower payment, same term) — ask yours.
Are taxes and insurance included?
No — this is principal + interest only. Real mortgage payments often add property tax, homeowner's insurance and PMI (together called PITI).
Is there a penalty for paying early?
Most modern mortgages have none, but some loans do. Check your note — a prepayment penalty directly reduces the savings shown.
Is my data sent anywhere?
No. Everything is computed in your browser; nothing leaves your device.
Disclaimer: Estimates for illustration, computed in your browser — no data leaves your device. Actual loans include fees, taxes, insurance and lender-specific rounding. We do not quote live rates. Verify with your lender before borrowing.