Extra Mortgage Payment Calculator
See exactly what paying more does to your mortgage. Add an extra amount each month, or switch on biweekly mode to pay half your payment every two weeks, and the tool shows the years saved, the interest saved and your new payoff date.
Extra Payment Calculator
Enter where your mortgage stands today, then add an extra payment or switch on biweekly mode.
6 years 9 months
off your mortgage, saving $118,972 in interest
An estimate covering principal and interest only. Property tax, insurance and any escrow shortfall are not included.
We don't store your inputs. No sign-up required.
Your Balance, With and Without Extra Payments
The orange line is your mortgage on its current schedule. The green line is the same mortgage with the extra payment or biweekly schedule you entered above. The dashed marker is the month the accelerated loan reaches zero.
The gap between the two lines widens for years before it narrows. That is the compounding at work: a smaller balance this month means a smaller interest charge next month, so more of your regular payment starts landing on principal too. The extra payment keeps paying you back long after you make it.
If you have not worked out your base payment yet, start with your base payment in our full mortgage calculator, which includes property taxes, insurance and PMI.
Every figure on this page comes from the same amortization maths your servicer uses, and the guidance is checked against published material from the Consumer Financial Protection Bureau on prepayment penalties. More about who we are.
Estimates for information only, not financial advice. Results depend entirely on the numbers you enter and assume a fixed rate with no fees. Confirm your balance, rate and prepayment terms with your servicer before changing what you pay. See our full disclaimer.
Do extra mortgage payments go to principal?
Yes — but only if the money is applied the right way, and that is not always automatic.
Your scheduled payment already covers the interest accrued that month plus a slice of principal. Anything above it has no interest left to cover, so it comes straight off the balance — no fee, no renegotiation, and the saving compounds for the rest of the term.
The problem is what happens inside the servicer's system. Send $200 extra with no instruction and it may be treated three ways:
- Applied to principal. What you want. The balance drops immediately and next month's interest is smaller.
- Held as unapplied funds. The money sits in a suspense account until it adds up to a full payment. It is still yours, but it is not reducing your balance or your interest while it waits.
- Treated as an early payment. The servicer credits it against next month's bill and marks you paid ahead. This feels helpful and saves you almost nothing, because the balance is unchanged.
Only the first shortens your loan. Most portals have a principal-only field; if yours does not, call and ask how to designate it. Some servicers also need standing instructions so every future overpayment is handled the same way, not just the first.
Verify once, then trust it. After your first extra payment, check the next statement. The principal balance should have fallen by your scheduled principal plus the full extra amount. If it has not, the money was not applied to principal — ring them before making a second one.
Biweekly vs one extra monthly payment
Biweekly sounds like a different strategy. Mechanically it is the same one on a different timetable.
There are 52 weeks in a year, so paying half your mortgage every two weeks means 26 half-payments — which is 13 whole payments, not 12. The extra payment is not a bonus for switching schedules; it is built into the calendar, and most people never notice they are making it.
So the honest comparison is against taking one monthly payment, dividing it by twelve, and adding that to each month's cheque. Here is a $300,000 mortgage at 7% with 30 years remaining under all three approaches:
| Approach | What you pay | Time to payoff | Total interest | Interest saved |
|---|---|---|---|---|
| Scheduled only | $1,995.91/mo | 30 years | $418,527 | — |
| Biweekly | $997.95 every 2 weeks | 23 years 9 months | $315,139 | $103,388 |
| Extra monthly (1/12th) | $2,162.24/mo | 23 years 9 months | $316,102 | $102,424 |
The two acceleration rows land within $964 of each other across a 24-year payoff — a rounding error on a loan this size. Biweekly edges ahead only because the money arrives a fortnight sooner each cycle, not because the method is cleverer.
So choose on practicality, not arithmetic:
- Paid fortnightly? Biweekly matches your cash flow and takes no willpower once it is running.
- Paid monthly? A monthly top-up is simpler, and you can change or pause the amount whenever you need to.
- Watch the setup fee. Some servicers charge to enrol in biweekly billing, and third-party "mortgage accelerator" services charge more. Paying a fee to replicate something you can do for free with a standing order makes no sense.
One practical caution: a few servicers accept biweekly money but only disburse it monthly, holding your half-payments until a full one accumulates. That removes most of the timing benefit while keeping the fee. Ask whether payments are applied on receipt before signing up.
Do all lenders allow extra payments?
Most do, and on a standard US mortgage you can usually overpay freely. Prepayment penalties have become much rarer since the post-2008 rules on qualified mortgages, which sharply restricted them.
Rarer is not the same as gone. Penalties still appear on some non-qualified mortgages, investor and portfolio loans, and older notes. Where one exists it is usually limited to the first few years and charged either as a percentage of the balance repaid or as a set number of months' interest.
Three checks settle it in about ten minutes:
- Read your note or closing disclosure. There is a specific prepayment section, and the closing disclosure has a plain yes/no box for whether your loan carries a penalty.
- Ask the servicer directly. Two questions: "does my loan have a prepayment penalty?" and "how do I make a principal-only payment?" Ask for the answer in writing or by secure message so you have a record.
- Confirm how extra money is applied by default. This matters more than the penalty question for most borrowers, because the default is often not principal-only.
Even where a penalty exists, many allow you to repay a share of the balance each year — often around 20% — before anything is charged, which is far more than most people overpay anyway. The figure is in your paperwork.
Overpaying is not always the best use of the money. If you carry credit-card debt at 20%+ or have no emergency fund, those come first — a mortgage at 7% is not your most expensive problem. And money sent to your mortgage is hard to get back without selling or refinancing. The CFPB's explanation of prepayment penalties is worth reading before you commit.
If you are weighing overpaying a mortgage against clearing another balance first, our debt payoff calculator compares the snowball and avalanche orders across every debt you hold.
What different extra payments are worth
Using this page's default loan — $320,000 at 7% with 30 years remaining, where the scheduled payment is $2,128.97 and the loan would otherwise cost $446,428 in interest:
| Extra per month | Payoff shortened by | Interest saved |
|---|---|---|
| $50 | 2 years 2 months | $38,666 |
| $100 | 3 years 11 months | $70,182 |
| $200 | 6 years 9 months | $118,972 |
| $300 | 9 years | $155,390 |
| $500 | 12 years 3 months | $206,857 |
Notice the shape: the returns are strong but not linear. The first $100 buys nearly four years; the second $100 adds under three more. Early dollars do the heaviest lifting because they cancel the most remaining interest.
That is also why timing beats size. An extra payment in year one removes interest from every one of the 29 years that follow. The same payment in year 25 removes almost nothing. If you can only overpay for a while, do it early rather than waiting until it feels affordable.
Frequently Asked Questions
They do, but only when the money is applied as a principal-only payment. Your scheduled payment already covers the interest due that month, so anything above it reduces the balance directly. The catch is that some servicers park extra money as unapplied funds or treat it as an early payment of next month's bill, which saves nothing. Mark the payment principal-only and check your next statement shows a lower balance.
The two land in almost the same place. Biweekly means 26 half-payments a year, which equals 13 monthly payments instead of 12, and spreading that same extra payment across the year as a monthly top-up gives a nearly identical result. On a $300,000 loan at 7% the gap between the two is under $1,000 of interest across the whole term. Choose whichever matches your pay cycle, and check your servicer does not charge a fee to set up biweekly billing.
Most do, and prepayment penalties are now rare on conforming US mortgages. They are not extinct, though: some non-qualified, investor and older loans still carry a penalty, usually limited to the first few years. Check your note or closing disclosure for a prepayment clause before you start, and ring your servicer to confirm how to send a principal-only payment.
More than most people expect, because every extra dollar lands on principal and removes the interest it would have generated for the rest of the term. On a $320,000 mortgage at 7% with 30 years left, $100 a month takes nearly four years off and saves about $70,182. Doubling that to $200 takes off 6 years 9 months and saves $118,972. Even $50 a month saves roughly $38,666.
How These Figures Are Calculated
The scheduled payment uses the standard fixed-rate amortization formula on the balance, rate and remaining term you enter. Both schedules are then walked month by month — interest charged on the outstanding balance, the payment applied, the balance reduced — rather than estimated with a shortcut, so the payoff month and the interest total are exact for the inputs given.
A note on the biweekly rate convention. The monthly schedule accrues interest at APR ÷ 12, so the biweekly schedule accrues at APR ÷ 26 — the same "annual rate divided by periods per year" rule. Modelling fortnightly interest on a daily basis instead would report roughly $2,800 more saved on this page's example loan. Real servicers differ on which they use; we chose the convention that keeps the two modes directly comparable with each other rather than the one that flatters biweekly.
Balances, rates and terms are figures you supply. We do not check your statements or contact your servicer. The 7% used throughout is an illustrative rate chosen to keep the arithmetic easy to follow, not a quote or a forecast. Results cover principal and interest only: property tax, insurance, PMI, HOA dues and any escrow shortfall sit outside the calculation, as do fees, rate changes and prepayment penalties.
Payoff dates are counted forward from the current month and rounded to whole months. Table figures are rounded to the nearest dollar, so a total may differ by a dollar from the sum of its parts.
Related Calculators
These free tools cover the rest:
- Mortgage Calculator — your full monthly payment with taxes, insurance and PMI.
- Amortization Calculator — the payment-by-payment schedule behind these figures.
- Loan Calculator — payment and interest on a personal or student loan.
- Debt Payoff Calculator — snowball and avalanche across every balance you hold.
- Home Affordability Calculator — what price range your income supports.
- Budget Calculator — where the extra payment comes from each month.
- Net Worth Calculator — every dollar off the mortgage lifts this by the same amount.
- All Calculators — every free tool on the site in one place.
- About — who writes this site and how the tools are built.
- Disclaimer — the limits of what these estimates can tell you.