Enter your mortgage and extra payment. See interest saved, years cut, and the wealth you build after payoff.
This calculator shows exactly how much interest you save — and how many years you shave off your mortgage — by making additional principal payments each month or as lump sums. It's for homeowners who want to pay off their mortgage faster and want to see the concrete dollar value of overpaying before committing to a higher payment.
Mortgages use amortization — each payment is split between interest (Balance × Monthly Rate) and principal (Payment − Interest). By adding extra principal payments, you reduce the balance faster, which reduces the interest portion of every future payment, which accelerates payoff in a compounding feedback loop. On a $350,000 mortgage at 7% over 30 years, paying an extra $300/month saves over $112,000 in interest and eliminates 8 years from the loan.
Mortgage overpayment is most powerful in the early years of a loan when a higher proportion of payments goes to interest. On a 7% mortgage, roughly 80% of early payments are pure interest. Every extra dollar paid in year 2 eliminates far more total interest than an extra dollar paid in year 25. Seeing this asymmetry is why most financial advisors recommend prioritizing early overpayments if you plan to stay in your home long-term.