Extra Payment Mortgage Calculator
Adding even a little to each payment goes straight to principal — shrinking the balance faster, cutting total interest, and shortening the loan.
Why extra payments work
Because interest is charged on the remaining balance, every extra dollar of principal you pay today saves all the future interest that dollar would have accrued. The earlier in the loan you do it, the larger the saving — which is why small, regular extra payments early on can remove years from the term.
Two ways to pay extra
- Recurring extra — a fixed amount added to every payment.
- Lump sum — a one-time payment (a bonus or tax refund) applied to principal.
Model it in Hearth
Set a recurring extra payment in Hearth and watch the payoff date move earlier and the total-interest figure drop in real time. The amortization schedule and charts update together, so you can compare "with" and "without" at a glance.
Try it on your own numbers
Free, no sign-up — move the sliders and watch it update live.
Open the calculatorFrequently asked questions
Do extra payments go entirely to principal?
Yes — an extra payment beyond your scheduled amount reduces the principal directly, which lowers the interest charged on every payment after it.
Is it better to pay extra monthly or as a lump sum?
Both help; what matters most is paying earlier. Regular extra payments compound over time, while a lump sum gives an immediate one-off drop in balance. Hearth lets you try either.
Will extra payments always save money?
They reduce interest and term, but check your lender allows prepayment without penalty first. The calculator shows the interest saved so you can weigh it against other uses of the money.