See what overpaying does
Type in your current mortgage details and your planned monthly overpayment. The mortgage overpayment calculator below works out your new payoff date and exactly how much interest you'd save.
You could save in interest.
Overpayment vs normal payments
Same mortgage, two stories. Run the numbers above and this table shows the difference side by side.
| Normal | With overpayment | |
|---|---|---|
| Hit "Calculate savings" to fill in this comparison. | ||
Related: Refinance Calculator · Personal Loan Calculator · Car Loan Calculator
Why overpaying punches above its weight
Here's the thing most people miss: your mortgage interest is charged on whatever you still owe, not the original loan. So every extra pound you throw at the balance early means next month's interest bill is a little smaller — and that saving quietly repeats every month for the rest of the loan.
That's why overpayments at the start of a mortgage do more heavy lifting than the same money paid years later. You're not just paying the loan down faster, you're shrinking the interest it can grow back. Want to see how the interest itself is worked out? Our interest calculator breaks it down, and the guide on how to calculate loan interest walks through the maths line by line.
Mortgage overpayment questions, answered straight
What is a mortgage overpayment?
Anything you pay on top of your normal monthly mortgage bill. Most lenders apply it straight to your balance, which means less interest charged next month, and the one after that. It snowballs.
How much interest can overpaying save?
It depends on your balance, your rate, and how much extra you pay. Small extras early in the loan make a bigger dent than big extras near the end. Punch your numbers into the calculator above and you get the exact figure for your mortgage.
Is there a penalty for overpaying?
Often, no. Many lenders let you overpay around 10% of the balance each year without charging you a penny. Go over that allowance and some will charge a fee, so check your mortgage terms before you start.
Should I overpay or save/invest instead?
Honest answer: it depends on the maths. If your mortgage rate is 5% and your savings pay 4%, overpaying usually wins. If your money could safely earn more elsewhere, investing might. That is a personal call — this calculator just shows the overpayment side of the equation.
Is this financial advice?
No. This calculator is a rough guide to help you see the numbers, not advice. Mortgage decisions are personal and the rules differ by lender and country, so talk to a proper adviser before changing anything.
Disclaimer: figures are estimates for guidance only, based on the numbers you enter. Actual results depend on your lender's terms, how they apply overpayments, rate changes, and fees. This is not financial advice.