How to Calculate Mortgage Repayments in the UK: Step-by-Step Guide

Introduction

Buying or remortgaging a UK home involves a string of calculations, from stamp duty and deposits to monthly repayments. Doing them before you speak to a broker or agent puts you in a much stronger position.

This guide explains how to calculate mortgage Repayments in the UK, step by step. Work out monthly repayments, total cost and total interest on a repayment mortgage. You'll see the formula, a fully worked example and practical tips for UK readers.

What this calculation covers

Work out monthly repayments, total cost and total interest on a repayment mortgage.

A few percentage points on LTV, rate or tax can change what you pay by thousands of pounds. Running the numbers early helps you set a realistic budget and compare deals properly.

The method and formula

We use the standard annuity formula: the same monthly payment covers interest and part of the balance so the loan is cleared at the end of the term.

Every figure on our mortgage Calculator follows this method, so you can check the working yourself.

Worked example

Here's a typical example using these figures:

Running them through the method gives:

The headline figure is monthly repayment: £1,389.58. Change any input and the result will move with it.

How to use the calculator

1. Enter or choose mortgage amount (£).
2. Enter or choose interest rate (%).
3. Enter or choose term in years.
4. Read your results. The main figure is shown at the top, with a breakdown underneath.
5. Try different values to compare scenarios side by side.

Tips for UK readers

• Stamp duty rules differ by nation: SDLT in England and Northern Ireland, LBTT in Scotland and LTT in Wales.
• Lenders price mortgages in LTV bands, so a slightly bigger deposit can unlock a noticeably lower rate.
• Always compare the total cost of a mortgage deal including fees, not just the headline rate.
• Most lenders let you overpay up to 10% of the balance each year without early repayment charges.

Frequently asked questions

What's the quickest way to work out mortgage Repayments?

Use our free mortgage Calculator. It applies this method automatically: We use the standard annuity formula: the same monthly payment covers interest and part of the balance so the loan is cleared at the end of the term.

Do these calculators cover Scotland and Wales?

Yes. We have separate calculators for LBTT in Scotland and Land Transaction Tax in Wales, as well as SDLT for England and Northern Ireland.

Are the mortgage figures a mortgage offer?

No. They are estimates. A lender's decision depends on your credit history, outgoings and their own affordability checks.

How accurate is the monthly repayment?

It uses the standard repayment formula and matches lender illustrations closely for a fixed rate, but actual payments can vary if your rate changes.

Summary

To work out mortgage Repayments, follow the method above: We use the standard annuity formula: the same monthly payment covers interest and part of the balance so the loan is cleared at the end of the term. For a quick, accurate answer with your own figures, use the calculator.

Next, read Mortgage Repayments: Common Mistakes, Tips and FAQs.