Mortgage Payoff Calculator
See how fast extra payments or a one-time lump sum would clear your mortgage — your new payoff date, the months you’d cut, and the interest you’d save.
Balance over time — current vs. accelerated
How you compare
🏡 See if a refi saves more
Compare ratesWhy prepaying works
Mortgage interest accrues monthly on your remaining balance. Extra principal shrinks that balance today, so every future month charges less interest — and because your payment is fixed, the interest you no longer owe converts directly into faster principal paydown. The effect compounds: the earlier the extra dollars arrive, the more months of interest they cancel.
How it’s calculated
We simulate the loan month by month: interest = balance × rate ÷ 12; principal = payment − interest. The baseline uses your current payment; the accelerated path adds your extra monthly amount and applies any lump sum to today’s balance. Savings = baseline interest − accelerated interest.
P&I only — escrow (taxes/insurance) doesn’t affect payoff. Estimates, not advice; confirm payoff quotes with your servicer.
Worked example
A $280,000 balance at 6.25% with a $1,850 P&I payment has about 24.9 years to run and $272,894 of interest ahead. Adding $200/month pays it off in 20 years flat — cutting 59 months and saving about $62,513.
Common mistakes
- Sending extra money without marking it “apply to principal” — some servicers treat it as an early next payment.
- Including escrow in the payment field — use principal & interest only.
- Prepaying a 6% mortgage while carrying 21% credit-card debt.
Where it is used
- Testing a payoff-by-retirement plan.
- Comparing a lump-sum windfall against monthly extras.
- Weighing prepayment against refinancing at today’s rates.
Frequently asked questions
How do extra payments pay a mortgage off early?
Every extra dollar reduces principal immediately, so all future interest is charged on a smaller balance. The payment stays the same, but more of each one hits principal — compounding your head start every month.
Should I pay off the mortgage or invest instead?
Paying principal 'earns' your mortgage rate risk-free. With the 30-year average at about 6.43% (Freddie Mac, Jul 2 2026), extra payments beat most guaranteed alternatives — but tax deductions, retirement matches, and higher-return investments can change the answer. Many people split the difference.
Do biweekly payments really help?
Yes, modestly: paying half your payment every two weeks makes 26 half-payments — one full extra payment a year. On a typical loan that trims several years of payments; model it here as extra monthly ≈ payment ÷ 12.
Will my lender charge a prepayment penalty?
Most U.S. conforming mortgages haven't carried prepayment penalties since 2014 rules took effect, but check your note — a few loan types still do. Also tell your servicer extra amounts are 'apply to principal', not 'advance the due date'.
Is a lump sum or monthly extra better?
Dollar-for-dollar, money applied sooner saves more interest, so a lump sum today beats the same total spread over years. The calculator accepts both — try each and compare the interest saved.