Mortgage Extra Payment Calculator
See how paying extra principal each month could shorten a fixed-rate mortgage and reduce the total interest you pay. You'll need your latest mortgage statement.
Your estimate
Enter your balance, rate and remaining term to see your estimate.
Estimated interest savings
Estimated time saved
Standard monthly payment (principal & interest)
Payoff period without extra payments
Payoff period with extra payments
Total interest without extra payments
Total interest with extra payments
How this calculator works
Monthly rate r = annual rate ÷ 12 ÷ 100; n = months remainingStandard payment = balance × r ÷ (1 − (1 + r)^−n) (balance ÷ n when the rate is 0%)Each month: interest = balance × r; principal paid = payment + extra − interestInterest savings = total interest without extra − total interest with extra
The calculator works through the loan one month at a time. The final payment is only what is still owed, so it is usually smaller than a regular payment.
Assumptions and limits
- Fixed-rate, fully amortizing loans with monthly payments only — not adjustable-rate, interest-only, or balloon loans.
- Property taxes, homeowners insurance, mortgage insurance, and escrow adjustments are excluded.
- Assumes every extra dollar goes to principal, with no prepayment penalty or other loan-specific restriction. Confirm how your servicer applies extra payments.
- The standard payment is calculated from your balance, rate and remaining term, so it may differ slightly from your statement.
- Doesn't compare other uses of the money (emergency savings, higher-rate debt, investing) or any tax effects.
This is an illustrative estimate, not a quote, a guarantee, or financial advice.
Your numbers stay in your browser — they are not sent to or stored by PocketWiseLab.