Extra Mortgage Payment Calculator
An extra payment goes entirely to principal, so it erases the interest that money would have cost for the rest of the loan. This calculator shows the interest and time you save, and compares several extra amounts side by side.
Use this extra mortgage payment calculator to see what a little more each month really buys you. Enter your loan, rate and term and an extra amount, and it simulates the loan to reveal your interest saved and years shaved off — plus a table comparing a range of extra payments so you can find the sweet spot.
Enter your loan, rate, term and an extra monthly amount, then press Calculate to see your savings and the comparison table.
How the extra payment calculator works
The magic of an extra mortgage payment is that all of it attacks the principal. Your regular payment is split between interest and principal, and early on it is mostly interest. An extra payment skips that split entirely — it comes straight off the balance, so the interest that balance would have generated for years to come simply disappears. This calculator rebuilds your scheduled payment from the loan, rate and term, then simulates the whole loan month by month with your extra applied, to measure exactly what you save.
To help you choose an amount, it also runs the simulation for a range of extra payments and lays them out in a comparison table, with your figure highlighted. If you would rather focus on a payoff date or model a one-off lump sum, the mortgage payoff calculator does that, and the biweekly mortgage calculator shows the popular “one extra payment a year” approach.
How the savings are calculated
where each figure comes from stepping the loan forward monthly:
- Payment — your scheduled principal & interest
- Extra — the additional principal you pay each month
- Interest — the sum of monthly interest until the balance is zero
Finding the right amount
There is no single “correct” extra payment — the comparison table exists precisely so you can see the trade-off. The savings do not rise perfectly in a straight line: the first extra dollars often deliver an outsized benefit because they cut the most interest-heavy early years, while very large extras run into diminishing returns as the loan shortens. A practical approach is to pick an amount you can sustain every month without straining your budget, since consistency matters more than a big one-off. Rounding your payment up to the next round number is a painless way to start.
What one (or two) extra payments a year does
One of the most searched strategies is simply making one extra mortgage payment a year — thirteen payments instead of twelve. It is popular because it feels manageable: set aside a twelfth of a payment each month, use a bonus or tax refund once a year, or switch to biweekly payments (26 half-payments equal 13 full ones). On a typical 30-year loan the effect is substantial, commonly trimming four to six years off the term and saving tens of thousands in interest, though the exact figure depends on your rate and how early you start. Two extra payments a year roughly doubles the acceleration, pulling the payoff in further still. To see your own numbers, take one month's payment, divide it by twelve, and enter that as your extra monthly amount above — that reproduces a single annual extra payment spread across the year.
Make it count
Two things protect the benefit. First, confirm the extra is applied to principal, not held toward the next payment — most servicers offer a principal-only option online. Second, check for a prepayment penalty, which a minority of loans carry in their early years. Beyond that, keep the bigger picture in view: an emergency fund and any employer retirement match usually come before extra mortgage payments, and if your mortgage rate is low, investing the money may serve you better. The calculator quantifies the mortgage side of that decision so you can compare it fairly.
Estimate only — not financial advice. Confirm your balance, rate and any prepayment terms with your lender before relying on the figures.
How to use it & key terms
Enter your loan, rate, term and an extra monthly amount, then press Calculate to see the interest saved, time saved and a table comparing several extra amounts.
| Term | What it means |
|---|---|
| Principal | The loan balance; extra payments reduce it directly. |
| Extra payment | An amount above the scheduled payment, applied to principal. |
| Interest saved | Interest avoided versus paying no extra. |
| Time saved | How much sooner the loan is paid off. |
| Principal-only | A payment directed entirely at the balance. |
| Prepayment penalty | A fee some loans charge for paying early — check yours. |
Sources & methodology
The calculator computes your scheduled principal-and-interest payment from the balance, rate and term with the standard amortization formula, then simulates the loan month by month — accruing interest, subtracting the payment plus the extra, until the balance clears — for your amount and for a set of comparison amounts. Interest saved and time saved are the differences from the no-extra baseline. Figures are principal and interest only and exclude taxes, insurance and any prepayment penalty.
Sources: Standard mortgage amortization formula and a month-by-month principal balance simulation.
Pay the mortgage down, or invest the difference?
Every spare amount you can put toward the mortgage forces a choice: send it to the loan, or invest it instead. There is no single right answer, but there is a clean way to think about it. Paying extra principal earns a guaranteed, tax-simple return equal to your mortgage rate — every dollar you prepay is a dollar that will never be charged interest again. That return is certain, which is rare and valuable.
Investing, by contrast, offers a return that may be higher over the long run but is uncertain and can fall in any given year. The comparison, then, is between a sure thing at your mortgage rate and an uncertain thing with a higher expected average. When your mortgage rate is high, the guaranteed saving is hard to beat and prepaying looks strong. When the rate is low, the odds tilt toward investing the difference — though the certainty and simplicity of debt reduction still appeal to many people regardless of the maths.
A few practical rules cut through the debate. First, capture any employer retirement match before making extra mortgage payments; a full match is an immediate return no prepayment can rival. Second, clear higher-rate debt — credit cards especially — before overpaying a lower-rate mortgage. Third, keep an emergency fund, because money sent to the mortgage is hard to get back without borrowing against the home. Prepayment is powerful but illiquid; savings stay flexible.
The mechanics are what make extra payments so effective. Because your scheduled payment is fixed, every additional dollar skips the interest queue and lands entirely on principal, shrinking the balance that all future interest is charged on. That is why an extra amount early in the loan removes far more interest than the same amount near the end. If your real goal is simply to be mortgage-free sooner, our mortgage payoff calculator shows the finish line each strategy reaches. Whichever path you choose, the worst option is usually indecision, which earns neither the guaranteed saving nor the market return.
Frequently asked questions
How much does an extra mortgage payment save?
It depends on your balance, rate and amount, but the effect is large because the extra goes entirely to principal. On a 30-year loan, an extra $200 a month can save tens of thousands in interest and shave several years off. The table shows savings at different amounts.
Where should extra payments be applied?
Always to principal. A principal-only extra reduces the balance immediately, so less interest accrues. If you send more without specifying, some servicers apply it to the next payment, which does not accelerate payoff — use the principal-only option.
Is paying extra worth it if I might move?
If you may sell or refinance soon, the long-run interest savings shrink, so extra payments matter less. But they still build equity faster, which is not lost when you sell. Weigh paying down debt against keeping cash liquid.
Does an extra payment reduce my monthly bill?
No. Extra principal shortens the loan and cuts interest, but your required payment stays the same until you recast or refinance. You finish sooner rather than paying less each month.
Is one extra payment a year the same as monthly extras?
Making one full extra payment a year — for example by paying biweekly — roughly matches spreading that amount across the year. Monthly extras apply a little sooner each cycle, so they save marginally more, but both work well.
Should I pay extra on the mortgage or invest instead?
Paying extra is a guaranteed, tax-free return equal to your rate. Investing might beat that but carries risk. Consider your rate, expected returns, taxes and emergency savings. Many fund a match and emergency fund first, then split the rest.
Will I be charged a prepayment penalty?
Most modern mortgages have none, but some do, particularly early on or on specific loan types. Read your documents or call your servicer before large extra payments so an unexpected fee does not erode the benefit.
How does the comparison table work?
It runs the same month-by-month simulation for several extra amounts, from zero up, and reports payoff time and interest saved for each. Your amount is highlighted so you can see how paying a little more or less changes the outcome.
What does one extra mortgage payment a year do?
Making one extra payment a year — thirteen instead of twelve — typically cuts about four to six years off a 30-year mortgage and saves tens of thousands in interest, depending on your rate and how early you start. Achieve it by paying a twelfth extra each month, paying biweekly, or with an annual lump sum. Divide one monthly payment by twelve and enter it as the extra above to model it.
What if I make two extra payments a year?
Two extra payments a year roughly doubles the effect of one, often shortening a 30-year loan by close to a decade and saving substantially more interest, depending on your rate. To model it, take two monthly payments, divide the total by twelve, and enter that as your extra monthly amount — and confirm each extra is applied to principal.