Mortgage Repayment Calculator
Work out the monthly cost and total interest on a UK capital-and-interest mortgage.
A £0 UK repayment mortgage at 0% over 0 years costs £0 per month and £0 in total interest over the term.
How repayment mortgages work
Same monthly, different split
Every month you pay the same amount. Early on most of it is interest; by the end most of it is capital. That's why overpayments in the first half save dramatically more interest than in the last half.
Term trade-off
Extending from 25 to 35 years cuts your monthly by 15–20% but roughly doubles the total interest. Only extend if affordability genuinely requires it.
Frequently asked questions
How is a UK mortgage repayment calculated?
Using the standard amortisation formula: Monthly = loan × (r × (1+r)^n) / ((1+r)^n − 1), where r is the monthly rate and n is total months. You pay the same amount each month; interest proportion falls, capital proportion rises.
Why does a longer term cost more in total?
Total interest scales with the years you hold the debt. A £200k mortgage at 4.6% costs about £123k interest over 25 years, or £166k over 35 years — with only ~£170/month saved on the monthly payment.
Does the rate apply for the whole term?
In the UK, almost always no. You fix for 2, 3, 5 or 10 years, then revert to the lender's SVR. Most borrowers remortgage onto a new fix to avoid the SVR. This calculator projects as if the rate held for the full term.
Is capital-and-interest cheaper than interest-only?
The monthly payment is higher, but you clear the debt. Interest-only has lower monthly cost but the full balance is still owed at the end — you need a separate repayment plan.
How much more am I paying vs rate of interest alone?
At 4.6% over 25 years, total interest is around 60% of the original loan. Push the rate to 6% and it approaches 90%. Sharp rates compound over time.
Reviewed by the Mortgage118 editorial team. Calculation assumes a fixed rate for the entire term — real-world UK mortgages typically fix for 2–10 years. Provides an estimate only.