Free calculator · 2026
UK mortgage overpayment calculator
See what overpaying does: the interest you'd save, the years it takes off your term, and your new payoff date. Overpaying shortens the term rather than lowering the payment. Nothing you type leaves your device.
Track it month after month
The UK Mortgage Tracker keeps your real balance, every overpayment and your live payoff date in one offline app, so the plan here becomes something you watch shrink.
How overpaying your mortgage works
When you overpay, the extra goes straight onto the balance, not the interest. Because interest is charged on a smaller balance every month after that, you save interest for the whole rest of the term, and the mortgage clears sooner. By default your monthly payment stays the same and the term shrinks, which saves the most interest. A small regular overpayment compounds into a surprisingly large saving over 20 or 25 years.
One thing to check: most lenders let you overpay up to 10% of the balance each year without penalty, but if you're on a fixed deal and go over that, an early-repayment charge can apply. Once your fixed period ends, the cap usually lifts. This is an estimate to plan with; your lender's exact terms and how they apply overpayments can vary.