Mortgage Affordability Calculator

How mortgage affordability is assessed

Lenders in the UK assess affordability using two main tests before issuing a mortgage offer: an income multiple test and a stress test. Both are required under FCA mortgage rules. This calculator applies both tests to give an estimate consistent with typical lender criteria.

Income multiples

The income multiple limits the loan to a set proportion of your gross annual income. Most lenders apply a standard multiple of 4 to 4.5 times your income. The Financial Policy Committee (FPC) caps the proportion of new mortgages above 4.5x income that lenders can write, to limit systemic risk. In practice, the cap means that loans above 4.5x are possible but less common. This calculator uses 4.5x as the standard multiple. If you have a high income, a strong credit profile, or a small number of financial dependants, some lenders may offer up to 5x or 5.5x through specific products.

The stress test

Lenders must also check that you could afford repayments if interest rates were to rise. The standard stress test uses the product rate plus 3 percentage points. If you apply for a mortgage at 4.5%, the lender tests affordability at 7.5%. The monthly payment shown in the calculator results is the stress-tested figure, which is why it may appear higher than the payment you would actually make at the headline rate. The stress test was introduced to protect borrowers from taking on mortgages that would become unaffordable if rates increased.

Other factors lenders consider

Beyond income multiples and the stress test, lenders carry out a detailed income and expenditure assessment. Monthly commitments, including credit card payments, car finance, personal loans, and childcare costs, reduce the amount lenders will offer. Employment type also matters: self-employed applicants typically need at least two years of accounts and may face stricter scrutiny of income stability. Your credit score and history affect which lenders are willing to lend and at what rate, though the score itself does not directly determine the income multiple applied.

Worked example

A single applicant earns £50,000 per year. They have a £25,000 deposit saved.

Maximum mortgage at 4.5x income: £50,000 x 4.5 = £225,000.

Maximum purchase price: £225,000 + £25,000 deposit = £250,000.

Stress-test monthly payment (at product rate + 3%): assuming the headline mortgage rate is 4.5%, the stress test runs at 7.5%. On £225,000 over 25 years at 7.5%, the monthly payment is approximately £1,663. The lender checks that this amount is comfortably within the applicant's monthly income after committed expenditure. The actual monthly payment at the headline rate of 4.5% would be approximately £1,252.

Frequently asked questions

Can I borrow more than 4.5 times my income?

Some lenders offer income multiples of 5x or higher, particularly for higher earners or professionals in certain fields. The FPC cap limits the proportion of high loan-to-income mortgages a lender can write, so availability at these multiples is restricted. A mortgage broker can identify lenders most likely to stretch to a higher multiple based on your specific circumstances and income profile.

Does this calculator account for my existing debts?

No. The calculator uses only income and deposit to estimate the maximum mortgage. Existing credit commitments, including personal loans, car finance, and credit card balances, reduce the amount most lenders will offer in practice. If you have significant outstanding debts, the actual maximum mortgage may be lower than the figure shown.

What is the stress test rate and why does it matter?

Lenders are required to check you could afford repayments at a higher rate, typically the mortgage rate plus 3 percentage points. The monthly payment shown in the results is the stress-tested payment, which is why it may look higher than the payment you would actually make at the headline rate you entered. This test was introduced by the FCA to prevent borrowers from taking on mortgages they could not afford if rates rose.

Is this affordability estimate legally binding?

No. This calculator provides an estimate for guidance only. Only a formal mortgage offer from a lender constitutes a binding commitment to lend. A mortgage broker or lender carries out a full affordability assessment based on your complete financial picture, including credit checks, income verification, and expenditure analysis, before issuing an offer.

How does a joint application affect the maximum mortgage?

On a joint application, lenders typically use the combined gross income of both applicants and apply the income multiple to that total. For example, two applicants earning £35,000 and £25,000 have a combined income of £60,000. At 4.5x, the maximum mortgage would be £270,000. Both applicants' credit histories and existing commitments are assessed.

Can self-employed applicants use this calculator?

Yes, but with caveats. Self-employed applicants typically need to demonstrate at least two years of accounts, and lenders usually use the average net profit over those years rather than the headline turnover figure. If your declared income for tax purposes is lower than your actual earnings, the mortgage multiple may be applied to a lower figure than you expect.

What deposit do I need?

Most lenders require a minimum 5% deposit for a residential mortgage, though products at 5% deposit carry the highest rates. The LTV thresholds where rates improve most significantly are 10%, 15%, 25%, and 40% deposit. First-time buyers may access shared ownership with a smaller deposit, or joint borrower sole proprietor products to include parental income.

Does my credit score directly affect the income multiple?

Your credit score does not change the income multiple applied, but it does determine which lenders are willing to consider your application at all. Lenders with the most competitive rates typically require a clean credit history. County court judgements (CCJs), defaults, or recent missed payments may limit you to specialist lenders at higher rates, or require a larger deposit to compensate.

Should I use a mortgage broker?

A mortgage broker has access to deals from across the market, including some not available directly to consumers. They can advise on which lenders are most likely to approve your application given your income type, credit history, and deposit, and can help you find the most competitive rate for your circumstances. Many brokers charge a fee, though some are paid by commission from lenders.

What is a shared ownership mortgage?

Shared ownership lets you buy a share of a property (typically 25% to 75%) and pay rent on the remaining share. The mortgage is taken out on the share you buy rather than the full property value, which reduces the loan needed. You pay both a mortgage on your share and rent to the housing association. You can buy additional shares over time (known as staircasing) up to 100% ownership.

Source: FCA Mortgage Conduct of Business Sourcebook (MCOB); Bank of England Financial Policy Committee mortgage rules.

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