Extra Mortgage Payment Calculator
How much time and interest an extra amount added to every monthly payment actually saves.
Every calculation runs locally in your browser. Assumes the extra amount is applied consistently every month for the life of the loan, with no prepayment penalty.
Without extra payments
360 months
$347,515 total interest
With $200/mo extra
279 months
$256,341 total interest
Interest saved
$91,173
Payoff 81 months (6.8 years) sooner
For informational and educational purposes only — not financial, investment, or tax advice, and not a substitute for consulting a qualified professional about your specific situation. TrueMeasureKit is not liable for decisions made based on these results. See our Terms of Service.
Why a small extra payment has an outsized effect
Every dollar paid beyond the required monthly payment goes straight to principal, since that month's interest is already covered — and a lower principal balance means less interest accrues every month after that, compounding for the rest of the loan. That's why a relatively modest extra payment early in a 30-year loan can shave years off the payoff timeline: it's chipping away at the balance during the years when the loan is carrying the most interest.
Frequently asked questions
Does the extra payment go entirely to principal?
This calculator assumes it does, which is how most lenders apply a clearly designated extra payment — but confirm with your servicer, since some require you to specify 'apply to principal' or they'll apply it to next month's payment instead.
Are there any downsides to paying extra toward my mortgage?
Check for a prepayment penalty (rare on modern mortgages but worth confirming), and weigh it against other uses for the money, like a higher-interest debt or retirement contributions that might have a better expected return.