Mortgage Overpayment Calculator
Paying a little extra on your mortgage every month can cut years off your loan and save tens of thousands in interest. Enter your loan details below and move the extra-payment field to see the effect instantly. The output includes a full amortization schedule comparing the standard and overpayment paths.
Standard monthly payment
$1,267
Interest saved
$56,562
Time saved
7y 3m
Balance over time
Amortization schedule (yearly)
| Year | Interest | Balance |
|---|---|---|
| 1 | $915 | $243,517 |
| 2 | $890 | $236,736 |
| 3 | $863 | $229,643 |
| 4 | $836 | $222,225 |
| 5 | $807 | $214,466 |
| 6 | $776 | $206,350 |
| 7 | $745 | $197,862 |
| 8 | $712 | $188,983 |
| 9 | $677 | $179,697 |
| 10 | $641 | $169,984 |
| 11 | $603 | $159,825 |
| 12 | $563 | $149,199 |
| 13 | $521 | $138,085 |
| 14 | $478 | $126,461 |
| 15 | $433 | $114,302 |
| 16 | $385 | $101,585 |
| 17 | $335 | $88,283 |
| 18 | $283 | $74,371 |
| 19 | $229 | $59,819 |
| 20 | $172 | $44,599 |
| 21 | $113 | $28,680 |
| 22 | $50 | $12,030 |
| 23 | $2 | $0 |
Compare scenarios
Run the same calculation with two or three input sets side by side. Differences are highlighted; every number comes from the same tested formula as the calculator above.
| Input | Scenario A | Scenario B |
|---|---|---|
| Principal | ||
| Annual Rate Pct | ||
| Term Years | ||
| Extra Monthly |
How it works
The calculator first computes your standard monthly payment using the amortization formula: payment = P × r / (1 − (1 + r)⁻ⁿ), where P is the principal, r the monthly interest rate and n the number of months.
It then simulates the loan month by month twice: once with the standard payment, once adding your extra monthly payment. Interest accrues on the remaining balance each month, so every extra dollar paid reduces all future interest.
The difference between the two simulations gives you the months saved and the total interest saved. The amortization table shows the balance trajectory with your overpayment applied.
Frequently asked questions
Is it worth overpaying my mortgage?+
Financially, overpaying is equivalent to a known, fixed, tax-free return equal to your mortgage rate. If your rate is 5%, overpaying beats any savings account paying less than 5% after tax. Check first whether your lender charges early-repayment fees.
Do extra payments reduce my monthly payment or the term?+
This calculator assumes extra payments shorten the term while the monthly payment stays the same — that is the option that saves the most interest. Some lenders instead recalculate (lower) your monthly payment; ask which options your contract allows.
How accurate is this calculator?+
It uses the standard amortization formula with monthly compounding, the same method most lenders use. Actual figures can differ slightly due to daily interest accrual, fees, or rate changes on variable mortgages.
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