UK Mortgage Affordability Calculator

Before you start viewing properties, it helps to have a realistic idea of how much you could actually borrow. This calculator estimates your maximum mortgage and property price based on your income, any joint applicant's income, your existing debt commitments and your deposit, using the income-multiple approach most UK lenders start from.

How to use the mortgage affordability calculator

Enter your annual income, and your partner's or co-applicant's income if you are buying together. Add up any existing monthly debt commitments, such as car finance, personal loans, credit card payments or buy-now-pay-later instalments, and enter your available deposit. The calculator applies a typical income multiple, currently set to 4.5x, which you can adjust, along with an interest rate and mortgage term, to estimate your maximum loan, maximum property price and monthly repayment.

How the calculation works

Lenders typically cap standard mortgage borrowing at around 4 to 4.5 times annual income, though this varies by lender and can be higher for some higher earners. This calculator starts from that income-multiple cap, then reduces it to reflect your existing monthly debt commitments, since every pound committed elsewhere is a pound a lender assumes is unavailable for a mortgage payment. Your deposit is then added to the resulting maximum loan to give an estimated maximum property price.

The calculator also applies a stress test, showing what your repayment would look like at a rate slightly higher than the one you entered. Real lenders do this too, to check you could still afford your mortgage if interest rates rose after completion, so the stress-tested figure gives you a sense of the safety margin built into a typical affordability assessment.

Worked example

Take a couple with a combined annual income of £70,000 (£38,000 and £32,000), £150 a month in existing commitments, and a £30,000 deposit, using the default 4.5x income multiple. Their income-multiple cap is £70,000 × 4.5 = £315,000. Their £150 monthly commitment reduces this by roughly £8,100, giving an estimated maximum loan of £306,900, and an estimated maximum property price of £336,900 once their deposit is added.

At a 4.5% interest rate over a 25-year term, that loan works out at roughly £1,706 a month. Stress-tested at 5.5%, the same loan would cost closer to £1,885 a month, which is the kind of buffer a lender wants to see you could absorb. Try adjusting the income, deposit and existing commitments in the calculator above to see how your own numbers change the outcome.

Common mistakes to avoid

A common mistake is treating the income-multiple figure as a guaranteed offer rather than a starting estimate. Lenders run a full affordability assessment covering your regular spending, dependants, credit history and employment type, so two applicants on the same income and with the same deposit can still be offered noticeably different amounts.

Another mistake is forgetting to account for all existing debt when budgeting, particularly car finance and buy-now-pay-later balances, which are easy to overlook but are treated seriously by lenders. It is also worth remembering that the maximum you can borrow is not necessarily the maximum you should borrow: building in some headroom for a change in circumstances, or a period of higher interest rates, makes for a more comfortable budget than stretching to the absolute limit.

Finally, remember that buying a home involves costs beyond the mortgage itself, including stamp duty, legal fees, survey costs and moving expenses, all of which need to come from your own funds alongside the deposit rather than from the mortgage.

Getting ready to buy

Once you have a realistic budget in mind, our mortgage calculator can work out the exact monthly repayment, total interest and full amortisation schedule for a specific property price and deposit. It is also worth checking your take-home pay to see what proportion of your net income a mortgage repayment would represent, and using our savings goal calculator if you are still building up your deposit. Our guide to first home buying costs and our mortgage deposit guide cover the wider costs and deposit options first-time buyers should plan for beyond the headline mortgage figure.

Related calculators

If you are carrying existing debt that could affect your affordability, our credit card payoff calculator can help you plan a route to clearing it before you apply. This calculator is a planning tool only: for a precise agreement in principle, speak to a mortgage broker or lender directly.