Extra Mortgage Payment Calculator
Add an extra monthly amount, a one-time lump sum, or both — and see your new payoff date and the interest you save.
P&I only — escrow for taxes and insurance continues regardless. Mark extra amounts "apply to principal".
How extra principal payments work
Your interest each month is computed on the remaining balance. Every extra dollar of principal permanently removes that dollar from every future month’s interest calculation — which is why modest extras produce outsized savings on long loans:
Worked example
$280,000 at 6.5% with a $1,769.79 payment (30-year schedule): adding $200/month pays the loan off about 7 years 4 months sooner and saves over $100,000 of interest. Even $50/month moves the payoff by years — test your own numbers above, including lump sums.
Getting the mechanics right
- Mark it “principal only.” Unlabeled extra money may be applied as an early next payment (saving nothing) or parked in escrow. Use the servicer’s principal-payment option and verify on the next statement.
- Earlier beats later: a lump sum in year 2 saves far more than the same sum in year 20, because it stops compounding for longer.
- Prepayment penalties are rare on post-2014 conforming loans, but scan your note once.
- Your required payment doesn’t drop. Prepaying shortens the loan. If you want a lower payment on the same term, that’s a recast (lump sum + small fee, keeps your rate) or a refinance.
Should the money go here at all?
- Pay high-interest debt first — a 22% card outranks a 6.5% mortgage by miles.
- Keep the emergency fund funded — home equity is illiquid; you can’t un-prepay to cover a job loss.
- Compare against investing: prepaying returns your mortgage rate, guaranteed and tax-free. At 6.5%+ that competes with long-run market averages on a risk-adjusted basis; at a 3% pandemic-era rate, investing usually wins on paper.
- Don’t skip the employer 401(k) match — an instant 50–100% return beats any mortgage math.
Frequently asked questions
What does one extra $100 a month do on a typical mortgage?
On a $280,000, 6.5%, 30-year loan: roughly 4 years faster and about $50,000+ of interest saved. The higher your rate and the longer your remaining term, the bigger the effect — enter your loan above for exact numbers.
Is one big annual payment as good as monthly extras?
Almost — twelve $200 monthly extras beat one $2,400 payment made at year-end by a small margin (the money arrives earlier on average). Make the annual payment in January rather than December and the gap nearly closes. Consistency matters more than form.
Extra payments vs. recasting — what’s the difference?
Extra payments shorten your term and total interest while the required payment stays the same. A recast applies a lump sum, then re-amortizes the smaller balance over the original term — lowering your required monthly payment instead. Recast for breathing room; prepay for speed.
Do extra payments change next month’s required payment?
No (except in rare simple-interest daily loans). The contract payment stays fixed; what changes is the split — after a prepayment, more of each payment is principal because the interest portion shrank with the balance.
Last reviewed: 2026-08-20 · Report an issue