Mortgage Extra Payments Calculator - Payoff Savings

A mortgage extra payments calculator shows how paying more than the scheduled installment can reduce a home loan’s interest cost and payoff time. Use the original loan amount, annual interest rate, and term, then choose whether regular payments are monthly or biweekly. You can add an extra contribution on a monthly, biweekly, or annual basis and optionally supply a current balance and months already paid. The results show the regular installment, the estimated payoff time, interest saved, and the number of months removed from the schedule. The regular payment is calculated with the fixed-rate amortization formula, P × r ÷ (1 − (1 + r)^−n), where r is the interest rate per payment period and n is the number of periods. The calculator then steps through each remaining payment period: it charges interest on the outstanding balance and reduces principal by the regular payment plus the equivalent periodic extra payment. Annual, monthly, and biweekly extras are converted to a comparable per-payment amount. A second schedule without the extra payment provides the baseline interest and term for the savings comparison. A current balance replaces the original balance for the remaining-payoff estimate. If no balance is supplied, months already paid reduce the original amortization schedule before the comparison starts. Biweekly schedules use 26 payments per year, while monthly schedules use 12. This distinction matters because paying half the monthly amount every two weeks usually produces 13 monthly-payment equivalents per year. The output is an estimate of principal-and-interest payments; it does not include escrow, property tax, homeowners insurance, mortgage insurance, or a servicer’s specific posting rules. Use this tool to test a recurring amount you can sustain, a yearly bonus, or a change in payment frequency. Compare several cases instead of directing all spare cash to the mortgage without considering emergency savings, higher-interest debt, or retirement matching. Confirm that your loan accepts principal-only overpayments and ask your servicer how it applies them. The figures assume a fixed rate and a payment large enough to cover accrued interest.