How Much Can I Borrow? Borrowing Power Calculator UK

How mortgage borrowing power is worked out

UK lenders answer "how much can I borrow" with two separate tests, then lend whichever comes out lower. The first is the income multiple: your gross annual income times a set figure, most commonly 4.5. The second is affordability: they take your take-home pay, subtract your living costs and the payments on any existing debts, and check the surplus can cover the mortgage repayment. This calculator runs both. It shows the income-multiple ceiling, the affordability ceiling, and the estimated maximum mortgage, which is the lower of the two, plus the property price your deposit would reach and the loan-to-value that implies. One more limit sits behind those: mainstream lending stops at 95% loan-to-value, so a small deposit can cap the loan below both tests. The calculator applies that ceiling too.

The 4.5x income multiple, and its limits

The income multiple is the headline number, and 4.5 times gross income is the everyday standard. Some lenders stretch to 5 or 5.5 times for higher earners or specific professions, but they cannot do it for everyone. The Bank of England's Financial Policy Committee holds new mortgage lending at or above 4.5 times income to 15% of the market. Since July 2025 an individual lender can run above that share as long as the market-wide total stays within 15%, so larger multiples are rationed rather than routine. The multiple applies to income before tax, and for joint applicants it applies to the combined figure. The multiple field is adjustable, so you can model a specific lender's policy, but 4.5 is the sensible default.

Why the affordability check can override the multiple

Here is the part a simple "times your salary" sum misses. Passing the income multiple is not enough if your monthly budget cannot carry the repayment. Lenders take your take-home pay, remove your regular outgoings and the payments on loans and credit cards, and stress test the mortgage repayment at a rate above the one you will actually pay. That stress margin is a safety check for rising rates. When your commitments are high, the affordability ceiling drops below the income multiple and becomes the figure that binds. The tool flags which of the two is holding you back, so you know whether to focus on income or on clearing debt.

A worked example

Take a single applicant earning £45,000 a year, with £1,200 a month in living costs and no other debts, putting down a £40,000 deposit. The income multiple gives 4.5 times £45,000, which is £202,500. The affordability check works out the take-home pay of about £2,993 a month, subtracts the £1,200 of costs to find a £1,793 surplus, and back-solves a maximum mortgage at a stressed rate of 6.50% (the 5.50% rate plus a 1% stress margin), which comes to roughly £265,600. The lender lends the lower of the two, so the estimate is £202,500 and the income multiple is what binds here. Add the £40,000 deposit and the property budget is £242,500, an LTV of about 83.5%, comfortably inside the 95% ceiling. The repayment on that mortgage at the real 5.50% rate over 25 years is about £1,244 a month.

Why lenders differ

This is an estimate, and a deliberately transparent one. Real lenders vary in ways a single model cannot capture. They set their own income multiples, treat bonuses, overtime and self-employed income differently, apply their own affordability scoring, and weigh your credit history on top. Two lenders can be tens of thousands of pounds apart on identical inputs. Treat the figure here as a realistic starting budget, then confirm it with a lender or a mortgage broker.

Frequently asked questions