Bureau of Wealth

Mortgage Affordability Calculator: How Much Can I Borrow

By the Bureau of Wealth team Updated

This calculator is general information, not financial advice. Check your own figures with the provider or a qualified adviser before acting on them.

Enter your income, deposit and the income multiple a lender uses to see what you might borrow, the repayment, and its share of your take-home pay if rates rise.

Using 2026/27 rates rates checked 14 September 2026

Leave at 0 if you are buying alone.

Lenders set their own limits. Change this to match a lender’s quote.

Check the highlighted fields to see your results.

What this calculator assumes

  • The amount you might borrow is your combined income before tax multiplied by the income multiple you enter. Lenders set their own limits and check far more than income, so their figure can be lower or higher.
  • The mortgage is on a repayment basis with the same interest rate for the whole term and monthly repayments. Interest-only and part-and-part mortgages are not modelled.
  • Take-home pay deducts 2026/27 income tax and employee National Insurance from each applicant's income separately, as an employee with a standard tax code. Pension contributions, student loan repayments and self-employment are not included.
  • The share of take-home pay counts only the mortgage repayment and the monthly loan and credit card payments you enter. Bills, childcare and other living costs that a lender will look at are not included.
  • The price is the loan plus your deposit. Stamp duty, legal fees, survey costs, lender fees and moving costs all come on top.

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How the calculator works

The calculator starts with a simple income multiple: your yearly income before tax, plus a second applicant's if you are buying together, multiplied by the figure you enter. Adding your deposit gives the price that loan would reach, and dividing the loan by that price gives the loan to value.

It then works out the monthly repayment with the standard repayment formula, the same one behind a spreadsheet's PMT function, and repeats it at a higher rate to show what happens if rates rise by the number of points you choose. Finally, it estimates each applicant's take-home pay after income tax and National Insurance, and shows the repayment plus your credit payments as a share of it.

How lenders really decide

Under the Financial Conduct Authority's responsible lending rules in MCOB 11.6, a lender must assess whether you can afford the mortgage before it lends. It has to take full account of your income after income tax and National Insurance, your committed expenditure, and your household's basic essential spending and quality-of-living costs. It must also take account of the effect of likely future interest rate rises.

The FCA does not set an income multiple. Its guidance says a lender may choose to cap lending at a multiple of income, but it must still show the loan is affordable once income and spending are taken into account. That is why the multiple in the calculator is an assumption you can change: set it to the figure from a lender's quote or an agreement in principle.

A worked example

Two applicants earning £40,000 and £30,000 in England have a £35,000 deposit. With an income multiple of 4.5, they might borrow £315,000, reaching a price of £350,000 at 90% loan to value. Over 25 years at 4.5%, the repayment is £1,750.87 a month. If the rate rose by 3 points to 7.5%, it would be £2,327.82.

Their combined take-home pay is about £4,786.60 a month, so the repayment uses 37% of it, or 49% if rates rose. If they also paid £300 a month on a car loan, those shares would become 43% and 55%.

What changes the result

A lower multiple of 4 would mean borrowing £280,000 for a £315,000 home, with a repayment of £1,556.33 that uses 33% of take-home pay. A longer term lowers the repayment but raises the total cost: over 30 years the £315,000 loan costs £1,596.06 a month, but the interest rises from £210,261.69 to £259,581.14.

Using the result

Treat the borrowing figure as a starting point, not a promise. The share of take-home pay is the more useful number for you: after the repayment, you still need to cover bills, food, travel and savings. Try the rate rise test with a figure that would genuinely worry you, and check that the higher repayment still leaves enough.

A mortgage broker or lender can tell you what you could actually borrow. To see how much more a smaller or shorter loan would save, use the loan repayment calculator, and check the stamp duty calculator before you settle on a price.

Frequently asked questions

Is there a legal limit on how many times my salary I can borrow?

The FCA's rules do not set a fixed income multiple. Lenders may set their own caps, but they must still check that the mortgage is affordable given your income and spending.

Why does the calculator test a rate rise?

Lenders must take account of the effect of likely future interest rate rises when they assess affordability. Seeing the higher repayment helps you judge whether you could cope when a fixed rate ends.

Does a second applicant double what I can borrow?

Not necessarily. The calculator adds both incomes before applying the multiple, but a lender will also count both applicants' debts and spending, so the real figure depends on your household as a whole.

What does loan to value mean?

It is the mortgage as a percentage of the property's price. A £315,000 loan on a £350,000 home is 90% loan to value. A bigger deposit lowers it.

Why is my take-home pay different from my payslip?

The calculator only deducts income tax and National Insurance with a standard tax code. Pension contributions, student loan repayments, salary sacrifice or a different tax code will change the real figure.

Sources

Figures come from institutions millions of people rely on. How we keep calculators accurate.