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Mortgage Affordability Calculator — How Much Can I Borrow?

Get a realistic idea of how much a lender might let you borrow. Enter your household income, monthly debts and living costs, your deposit and the rate you expect to pay. The calculator tests three limits — an income multiple, your monthly budget at a higher stress-test rate, and your deposit — and shows the lowest one as your estimated borrowing and property budget.

How to use the Mortgage Affordability Calculator

  1. Enter your income and any partner’s income before tax, and choose where you live for tax purposes.
  2. Add your monthly debt payments, living costs and the spare money you want to keep each month.
  3. Enter your deposit, the interest rate you expect, the mortgage term and the lender assumptions.
  4. Read your estimated borrowing, property budget and which limit is holding you back.

How lenders decide what you can borrow

Lenders use two main checks. The first is an income multiple: most will lend somewhere between four and five and a half times your household income, depending on your circumstances. The second is affordability: they look at your outgoings and test whether you could still afford the mortgage if interest rates were higher.

This calculator estimates your take-home pay from your income, subtracts your commitments and living costs, and works out how large a loan your remaining budget could support at the rate you expect plus a stress-test buffer. Your estimate is the lowest of the three limits.

Ways to increase what you can borrow

Paying off credit cards, loans and car finance reduces your commitments and can increase the amount you can borrow. A bigger deposit raises the maximum loan allowed by loan-to-value and can unlock lower interest rates. Extending the term lowers the monthly payment, but increases the total interest paid.

Because each lender applies its own criteria, treat the estimate as a guide and speak to a mortgage adviser or ask for an agreement in principle before house hunting.

Assumptions & important information

  • Take-home pay is estimated from salary only, for the tax year you choose, with no pension contributions, student loan or other deductions.
  • The income multiple, stress-test buffer and maximum loan-to-value are assumptions you can change; each lender sets its own.
  • The estimate is the lowest of three limits: income multiple, budget at the stress-test rate and loan-to-value.
  • Credit history, employment type, age and the property itself are not considered.
  • Interest rates shown in the form are examples only, not current market rates. Enter the rates from your own quote.
  • This calculator gives estimates for information only. It is not financial advice and not a mortgage or loan offer. Rates, fees and lender criteria vary, so check the details with your lender or a regulated adviser. Your home may be repossessed if you do not keep up repayments on a mortgage or other debt secured on it.

Ideas & examples

  • £55,000 income, £40,000 deposit: Take-home pay is about £3,538 a month. At 4.5× income lenders might cap borrowing at £247,500, while a monthly budget stress-tested at 7.5% supports about £277,185.
  • Joint applications: Add a partner’s income to see how a joint application changes your budget. Both incomes count towards the income multiple and your household take-home pay.
  • Clearing debts first: Reducing a £200 monthly loan payment to zero adds £200 to the budget available for a mortgage, which can raise your borrowing by tens of thousands of pounds.

Frequently asked questions

How much can I borrow for a mortgage?

Most lenders offer around four to five and a half times your household income, subject to their affordability checks. This calculator estimates a figure from your income, outgoings and deposit.

What is a stress test?

Lenders check you could still afford your mortgage if interest rates rose. The calculator tests your budget at a higher rate that you can adjust.

Does this guarantee a mortgage?

No. Lenders look at your credit history, employment, other debts and the property itself. Use the result as a guide and ask for an agreement in principle.

Why is my estimate lower than four and a half times my income?

Your outgoings, debts or a smaller deposit may limit the amount, or your budget may not stretch to the payment at the stress-test rate. The calculator tells you which limit applies.

How is take-home pay estimated?

It uses the same Income Tax and National Insurance rules as our take-home pay calculator for the tax year you choose, with no pension or student loan deductions.

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