UK Mortgage Affordability Calculator

This calculator estimates how large a mortgage you could take on, based on your income and a lender income multiple. Fill in the fields and the results update as you type. There is no submit button.

1. Enter your annual income. Use your gross salary before tax. This is the main figure lenders use to size your mortgage.
2. Add a joint applicant income (optional). If you are buying with someone else, add their income. The calculator combines both incomes before applying the multiple.
3. Enter your deposit. This is the cash you can put towards the purchase. It does not change how much you can borrow, but it raises the maximum property price you can reach.
4. Set the income multiple. The default is 4.5, the most common UK starting point. Adjust it to match a specific lender if you know their cap.
5. Enter the interest rate and term. These drive the estimated monthly payment. A typical term is 25 years, though terms range from a few years up to 40.
6. Review your results. You will see the maximum you could borrow, your maximum property price, the estimated monthly payment, and your loan to value.

The calculator uses three clear steps. None of them rely on a hidden assumption, so you can reproduce every figure by hand.

Step one: maximum borrowing. Your income and any joint income are added together, then multiplied by the income multiple. In words: maximum borrowing equals total income times the income multiple. With a combined income of 60,000 and a multiple of 4.5, the maximum borrowing is 270,000.

Step two: maximum property price. Your deposit is added to the maximum borrowing. In words: maximum property price equals maximum borrowing plus deposit. So 270,000 of borrowing with a 30,000 deposit gives a maximum property price of 300,000.

Step three: estimated monthly payment. The payment uses the standard repayment mortgage formula. In words: the monthly payment equals the loan times the monthly interest rate, divided by one minus one plus the monthly rate raised to the power of minus the number of months. The monthly rate is the annual rate divided by 12, and the number of months is the term in years times 12. When the interest rate is zero, the payment is simply the loan divided by the number of months.

Loan to value. Finally, loan to value is the borrowing divided by the property price, shown as a percentage. In words: loan to value equals maximum borrowing divided by maximum property price, times 100. Borrowing 270,000 against a 300,000 price is a loan to value of 90 percent.

The headline figure is the maximum you could borrow. It is driven entirely by your income and the multiple, so the fastest way to increase it is to add a joint applicant or find a lender with a higher multiple. Increasing your deposit does not change this number.

The maximum property price is usually the more useful figure when house hunting, because it reflects both your borrowing and your deposit. If you want to afford a more expensive home, a larger deposit moves this figure up pound for pound.

The estimated monthly payment shows what the full borrowing would cost each month at the rate and term you entered. A longer term lowers the monthly payment but increases the total interest paid over the life of the loan. A higher interest rate raises the payment. It is worth checking that the payment is comfortable against your monthly budget, not just that the borrowing is available.

The loan to value tells you how much of the property is funded by the mortgage. Lower loan to value bands, such as 90, 85, 75, and 60 percent, typically attract better interest rates. If your loan to value is just above one of these thresholds, a slightly larger deposit could move you into a cheaper rate band.

Remember that this is an estimate. Real lenders run an affordability assessment that looks at your spending, existing credit commitments, and a stress test against higher rates. Use the result as a realistic starting point, then confirm with a lender or a mortgage broker.