Extra mortgage payment calculator
See exactly how a one-off extra payment, an annual top-up or a higher monthly rate compresses your mortgage timeline — and how much interest you avoid paying along the way.
Calculation runs in your browser — your inputs never leave the device.
Your inputs
Takes ~ 1 minuteYour result
Fill in the fields above and click Calculate — your personalised plan appears here in a moment.
What this calculator is useful for
See exactly how a one-off extra payment, an annual top-up or a higher monthly rate compresses your mortgage timeline — and how much interest you avoid paying along the way.
Use it before sending extra money to the lender. The calculator shows whether a one-off payment, regular top-up or higher monthly payment meaningfully reduces interest and time.
How to read the result
Interest saved is not the same as cash saved today. Extra payments can be powerful, but they also reduce liquidity and may compete with emergency funds, pensions or higher-interest debt.
What to check next
Check lender rules before acting. Some mortgages limit overpayments, charge early-repayment fees or require you to choose between lower instalments and a shorter term.
Plain-language notes
Use this section if the finance words on the page are new to you. The calculator is meant to support a decision, not to reward perfect terminology.
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Principal: the original debt or mortgage balance before interest is added.
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APR/interest rate: the yearly cost of borrowing. A higher rate usually makes debt more expensive and payoff slower.
What to compare
Compare at least two scenarios before trusting the first answer. A useful result should tell you what changes if income, costs, rates, or timing move.