Extra Payment Mortgage Calculator
See exactly how much faster you’ll be debt-free — and how much interest you’ll save — by adding a little extra to each payment. Enter your loan, then try different extra amounts.
Why extra payments are so powerful
On a fixed-rate mortgage, your scheduled payment is split between interest (charged on the remaining balance) and principal. Early on, most of it is interest. An extra payment goes 100% to principal — so it not only shrinks the balance, it erases all the future interest that balance would have generated. That compounding is why a modest extra amount can remove years from a 30-year loan.
Use the “Extra monthly payment” field above and watch three things change instantly: your payoff time, your total interest, and the “loan balance over time” chart, which now drops to zero noticeably sooner. The amortization schedule below shows the new month-by-month path, and you can download it as CSV.
How to use this calculator
Compare scenarios: try $50, $100 and $250 extra per month and note the payoff date and total interest for each. Pick the largest amount you can comfortably sustain — consistency matters more than size, because the earlier each dollar lands, the more interest it kills. The tool also shows a downloadable schedule, so you can see exactly which month your loan now ends.
How extra payments are applied
When you add money on top of your scheduled payment, that extra amount should go straight to principal, immediately lowering the balance that next month's interest is charged on. Because interest is recalculated on a smaller balance, every future payment then covers slightly more principal, creating a snowball that accelerates over time. This calculator assumes each extra dollar is applied to principal in the month you pay it — which is the most common and most beneficial treatment, but worth confirming with your lender, since some apply extra funds to the next scheduled payment instead, which does not save interest.
Why early extra payments matter most
Interest on an amortizing loan is front-loaded: in the early years the balance is large, so most of each scheduled payment is interest. A dollar of extra principal paid in year one erases interest that would otherwise have compounded across the entire remaining term, while the same dollar paid in the final year saves almost nothing. That is why starting early — even with a small amount — beats waiting until you can "afford more."
A worked example
Take a hypothetical $250,000 loan at 6.5% over 30 years, with a scheduled payment near $1,580. Add $200 extra each month from the start and the loan pays off in roughly 23 years instead of 30, saving on the order of $85,000 in interest. Make a single $10,000 lump sum in year one instead and you might trim two to three years and tens of thousands in interest — less than the steady monthly extra, but with no ongoing commitment. The exact figures depend on your rate and balance, so enter your own numbers above.
Three ways to pay extra
| Method | How it works | Best for |
|---|---|---|
| Extra monthly | A fixed amount added to every payment | Steady savers who want maximum, predictable impact |
| One-time lump sum | A single large principal payment | Windfalls, bonuses, or tax refunds |
| Biweekly payments | Half-payments every two weeks (≈13 full payments/year) | Paying a bit extra almost painlessly |
Tips and common mistakes
First, tell your lender the extra is for principal — label the payment or use the principal-only option, or it may simply advance your due date. Second, check for a prepayment penalty; most modern mortgages don't have one, but some loans charge a fee for paying off early. Third, mind opportunity cost: if you carry credit-card debt at a much higher rate, pay that first, and if your loan's rate is low, investing the money might earn more over time. Finally, keep an emergency fund intact — money sent to principal is hard to get back without refinancing, so don't over-commit cash you might need.
Frequently asked questions
How much does paying extra actually save?
It depends on your rate and how early you start, but on a typical 30-year loan even $100–$200 extra per month commonly cuts several years and tens of thousands in interest. Enter your numbers above for the exact figure.
Monthly extra vs one lump sum — which is better?
Both work. Monthly is easier to budget and saves interest every month; a lump sum makes a big one-time dent. Earlier is always better because interest accrues on the remaining balance.
Do extra payments lower my required payment?
No — they shorten the term, not the monthly amount. You finish sooner and pay less interest, but the scheduled payment stays the same unless you recast or refinance. A recast re-amortizes the lower balance over the original term to reduce the payment, usually for a small fee.
Will my lender apply the extra to principal?
It should, but not always automatically. Some lenders apply unlabeled extra money to your next scheduled payment, which doesn't save interest. Use the principal-only option or note "apply to principal" so the extra reduces your balance right away. Check your statement afterward to confirm.
Are there prepayment penalties?
Most modern mortgages have none, but some loans charge a fee for paying off early, especially within the first few years. Read your loan agreement or ask your lender before making large extra payments, so a penalty doesn't eat into your interest savings.
Should I pay extra or invest instead?
It depends on the rates and your other debts. Paying down the loan is a guaranteed, risk-free return equal to its interest rate. If you carry higher-interest debt like credit cards, clear that first; if your loan's rate is low, investing the money may earn more over time. Keep an emergency fund before committing cash to principal.
Last updated: July 2026 · How we calculate
BriskToolbox provides estimates for general information only and is not financial advice. Check that your lender applies extra payments to principal and charges no prepayment penalty.