Mortgage Payoff Calculator (Extra Payments)
See how much sooner you can pay off your mortgage and how much interest you can save by adding extra principal each month, a one-time lump sum, or switching to biweekly payments.
FINANCEFind out how much faster you can pay off your mortgage - and how much interest you can save - by sending extra principal each month, dropping a one-time lump sum, or switching to biweekly payments. Side-by-side comparison vs. the baseline schedule.
Enter your current loan balance, original APR, original term, and how many monthly payments you have already made - the calculator derives the regular monthly P&I and remaining term, then runs two amortization simulations: a baseline schedule with no extras, and an accelerated schedule with your extra monthly principal, optional one-time lump sum, and optional biweekly cadence. Worked example: $320,000 balance, 7% APR, 26 years remaining on a 30-year loan, adding $200 extra per month pays the loan off roughly 5.4 years early and saves about $83,000 in total interest. The biweekly trick (26 half-payments per year = 13 monthly payments) typically shaves 5-6 years off a 30-year loan with no other changes - you can replicate it for free by paying 1/12 extra each month or one extra payment per year.
Mortgage Payoff Calculator (Extra Payments)
See how much sooner you can pay off your mortgage - and how much interest you can save - by adding extra principal each month, a one-time lump sum, or switching to biweekly payments.
and save $84,975 in interest
| Baseline (no extras) | Accelerated | |
|---|---|---|
| Months to Payoff | 26 yr | 21 yr |
| Total Remaining Interest | $375,723 | $290,748 |
| Total Remaining Paid | $695,723 | $610,748 |
Note: if you itemize and deduct mortgage interest on Schedule A, your effective after-tax interest rate is lower than your APR. The interest savings shown here are pre-tax - itemizers will keep somewhat less of the benefit because they would have deducted some of that interest.
How Extra Mortgage Payments Work
In the early years of a mortgage, the bulk of each payment goes to interest, not principal. On a $320,000 balance at 7% APR, the very first month's interest is about $1,867 - on a $2,129 P&I payment, only $262 reduces principal. Every extra dollar you send straight to principal skips all the future interest that dollar would have generated, which is why even $100-$200 extra per month can cut years off the loan and save tens of thousands in interest.
The biweekly trick: instead of one full payment each month, pay half the monthly payment every 14 days. There are 52 weeks per year, so 26 half-payments = 13 full monthly payments per year - one extra payment baked in. On a 30-year mortgage, biweekly typically shaves ~5-6 years off the loan with no other changes. Many servicers charge a fee to set this up officially; you can replicate it for free by simply paying 1/12 extra each month, or making one full extra payment annually.
Should you prepay or invest the difference? At a 7% mortgage rate, prepaying gives you a guaranteed 7% after-tax return (or close to it - your effective rate is lower if you itemize and deduct mortgage interest). The S&P 500 has historically returned ~10% annualized, so investing the difference in a low-cost index fund typically wins over 20-30 years. But mortgage prepayment is risk-free, behaviorally easy, and reduces sequence-of-returns risk - especially valuable for people near retirement who want to enter retirement debt-free. Many advisors split the difference: invest in tax-advantaged accounts first, then prepay.
Estimates assume your extra payments are applied to principal immediately. Confirm with your loan servicer - some lenders apply unscheduled payments to pre-paid interest or hold them until the next due date unless you explicitly mark the payment "apply to principal."