Mortgage Payoff Calculator
The three most common ways homeowners pay a mortgage off early all do the same thing: send a little extra principal in. The shape of the extra payment changes the schedule but not the underlying math. Compare the three side by side and see how much time and interest each one actually saves on your loan.
What you still owe on the mortgage today.
Annual rate.
How long until your scheduled payoff. New 30-year? 30. Five years in? 25.
Each strategy is converted to a monthly equivalent so the comparison is apples to apples.
Applied on top of the regular payment each month.
$67,484 less interest at $200 extra/mo
4 yr 11 mo earlier
- Principal
- $290,000
- Interest paid (accelerated)
- $229,947
- Interest saved
- $67,484
- Baseline payoff
- 25 yr
- Accelerated payoff
- 20 yr 1 mo
- Baseline interest
- $297,430
Free during pilot
How early payoff works
Every dollar of extra principal you pay reduces the balance interest accrues against for every remaining month. The effect compounds: a smaller balance means less interest next month, which means more of the next regular payment goes to principal, which means a smaller balance the month after, and so on.
That's why early payoff has such a disproportionate effect when you start early — early-loan dollars stack up against decades of future interest. The same payment in year 25 saves comparatively little because most of the interest has already been paid by then.
How the three strategies compare
- Extra monthly. Add a fixed dollar amount to your payment every month. The most flexible — easy to start, stop, or adjust as your budget changes.
- Annual lump sum. Make one principal payment per year — tax refunds, bonuses, or year-end commissions. We model this as monthly principal of (lump / 12) so the schedule comparison stays apples-to-apples; in reality, the lump arrives once, so the time savings is slightly different than the calculator shows, but the interest savings is close.
- Biweekly (paying half your monthly payment every two weeks — gives you one extra payment a year). There are 26 biweekly periods per year (52 ÷ 2), which equals 13 full monthly payments. We model this as an extra (monthly P&I ÷ 12) per month.
Why we convert everything to "monthly principal equivalent"
Each strategy moves money to principal on a different cadence. The only way to compare them honestly is to convert each one to its equivalent monthly principal contribution and run the same amortization (how each monthly payment splits between interest and principal over time) with that adjustment. That's what the calculator does — which is why a $5,000 annual lump shows up the same as $416 / month of extra principal.
Tell your servicer what you mean
Most servicers default to applying any overpayment to the next scheduled payment, not to principal. If you want the schedule above to match reality, you usually need to:
- Designate the extra amount as "principal only" when you submit it through their portal, or
- Send a written letter with the next coupon stating the same, or
- Enroll in their official biweekly program (if they offer one — some charge a setup fee that's rarely worth it).
What this calculator deliberately excludes
- Prepayment penalties. Almost all U.S. owner-occupied loans originated after 2014 have no prepayment penalty, but it's worth checking your note.
- Lost-deduction effects. Faster payoff means less deductible interest, which can matter for high-income itemizers. The effect is real but usually small.
- Opportunity cost. Dollars sent to principal can't go to retirement accounts or other investments. If your loan rate is below your expected portfolio return, the math often favors investing instead.
Frequently asked questions
What is the fastest way to pay off a mortgage early?
Every early-payoff method works the same way — sending extra principal. Extra monthly is the most flexible; an annual lump sum uses bonuses or tax refunds; biweekly payments add up to one extra monthly payment a year. This calculator converts each strategy to its monthly-principal equivalent so you can compare the time and interest saved on equal footing.
How do biweekly payments save money?
Paying half your monthly payment every two weeks produces 26 half-payments a year — equal to 13 full monthly payments instead of 12. That one extra payment goes to principal, shrinking the balance faster. Some servicers charge a setup fee for official biweekly programs that is rarely worth it; you can replicate the effect yourself for free.
Does paying extra early save more than paying extra later?
Yes. Early-loan dollars stack against decades of future interest, while the same payment in year 25 saves comparatively little because most of the interest has already accrued. The effect compounds: a smaller balance means less interest next month and more of each payment going to principal.
Are there downsides to paying off a mortgage early?
Possibly. Dollars sent to principal cannot go to retirement accounts or other investments — if your loan rate is below your expected portfolio return, investing may come out ahead. Faster payoff also means less deductible interest for itemizers (usually a small effect), and you should confirm your note has no prepayment penalty (rare on owner-occupied loans originated after 2014).
Estimates only — not a payment schedule from your servicer. The math assumes a fixed rate and that every extra payment is correctly applied to principal on the same day each month. Most servicers require you to explicitly designate extra funds as "principal only," otherwise the surplus may be applied to the next regular payment or held in suspense. Methodology last reviewed: May 26, 2026.