Overview
This mortgage calculator works out your monthly repayments on a UK repayment mortgage, plus the total you'll pay back and how much of that is interest. Enter the amount you want to borrow, the annual interest rate and the term in years. You'll get an instant monthly figure and a full cost breakdown, and you can open a year-by-year repayment schedule to see how your balance falls over time. It's ideal for comparing deals, testing different terms, or checking how a rate change would affect what you pay each month.
How it's calculated
A repayment (capital-and-interest) mortgage is worked out with the standard amortisation formula. Each month you pay some interest on the outstanding balance plus a slice of the capital, so the balance — and the interest portion — shrinks over time.
We convert your annual rate to a monthly rate, and your term to a number of months, then solve for the fixed monthly payment that clears the balance exactly at the end of the term.
M = P · r · (1 + r)^n ÷ ((1 + r)^n − 1)
Where M = monthly payment, P = amount borrowed, r = monthly interest rate (annual rate ÷ 12), and n = number of monthly payments (years × 12).
Worked example
Take a £250,000 mortgage at 4.5% over 25 years:
| Amount borrowed | £250,000 | |
|---|---|---|
| Interest rate | 4.5% | |
| Term | 25 years (300 months) | |
| Monthly repayment | ≈ £1,390 | |
| Total repaid | ≈ £416,900 | |
| Total interest | ≈ £166,900 |
So you'd pay about £1,390 a month, and over 25 years roughly £166,900 of that is interest. Shortening the term raises the monthly payment but cuts the total interest substantially — try it above.
Current rates & key facts
UK mortgage rate context
| Item | Rate / note |
|---|---|
| Bank of England base rate | 3.75% (held 18 June 2026) |
| New fixed-rate deals | Priced as a margin over base rate; vary by lender, LTV and fix length |
| Standard Variable Rate (SVR) | Set by each lender; usually higher than a fixed deal |
Mortgage pricing changes frequently and depends on your loan-to-value, credit profile and the specific deal. Always compare current rates from lenders or a fee-free broker.
Last updated 18 June 2026 · Source: Bank of England — Bank Rate