Mortgage Calculator

What this calculator does. It estimates the monthly repayment on a mortgage, plus the total amount you'll repay and how much of that is interest. You can use it for a new mortgage, a remortgage, or just to see how a different rate or term would change your monthly cost.

How the calculation works. We take the loan amount, annual interest rate and term in years and apply the standard repayment formula used by lenders. The annual rate is split into twelve monthly periods, and each monthly payment covers both interest on the remaining balance and a slice of the balance itself. Early in the term most of your payment goes on interest; later, more of it chips away at what you owe. If you choose interest-only, your monthly figure only covers the interest — the original balance still has to be repaid at the end.

A worked example. On a £250,000 repayment mortgage at 5% over 25 years, the estimated monthly payment is around £1,461. Over the full term you'd repay roughly £438,000 — meaning about £188,000 of that is interest. Shortening the term to 20 years pushes the monthly payment up to around £1,650, but cuts total interest by tens of thousands of pounds.

How to read the results. "Monthly payment" is what leaves your account each month. "Total repaid" is everything you'll pay across the term, and "Total interest" is the cost of borrowing. Try changing the rate by 1% or the term by 5 years to see how sensitive your payment is — it's a quick way to stress-test affordability.

Figures are estimates only. Your actual offer depends on the lender, product fees, your deposit and your circumstances.