Mortgage Affordability Calculator

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How to use this calculator

This gives you a starting estimate to plan around — not a mortgage offer or a lender’s actual decision.

The method

How lenders decide how much you can borrow

Most UK lenders start from an income multiple: MoneyHelper states that lenders “typically cap the maximum amount you can borrow at four and a half times your annual income,” adding that “most people are offered less, so keep this in mind when planning your budget.” For joint applications, this multiple is applied to your combined income, not each income separately.

Some lenders offer higher multiples — reportedly up to 5.5x or 6x — to specific income bands, larger deposits, or particular schemes, but these vary by lender and aren’t guaranteed, which is why this tool treats anything above 4.5x as an illustrative “if a lender offers more” option rather than a typical figure.

The regulatory backdrop

The loan-to-income “flow limit”

Since 2014, the Bank of England has run a market-wide rule limiting how much high-multiple lending banks can do in total: no more than 15% of a lender’s new mortgages can be extended at 4.5x income or more. This is a constraint on lenders, not a personal borrowing limit on you — it doesn’t stop an individual lender offering you more than 4.5x, it just limits how much of that lending they can do overall.

This rule was under active regulatory review as of 2026 (a Bank of England/FCA consultation proposed changing how the 15% cap is applied across the market), so the exact mechanics may change — the underlying idea (a market-wide check on high-multiple lending) is the stable part.

Affordability rules

What lenders must check beyond the income multiple

UK lenders are required by the Financial Conduct Authority to run a genuine affordability assessment, not just apply a multiple. FCA rules (MCOB 11.6) require a lender to assess your net income, your existing committed spending, your essential living costs, and — for mortgages fixed for under 5 years — your ability to cope with future interest rate rises for a minimum of 5 years.

Between 2014 and August 2022, this rate-rise check used a fixed stress margin (roughly 3 percentage points above the reversion rate) set by the Bank of England’s Financial Policy Committee. That specific fixed margin was withdrawn in August 2022, giving lenders more flexibility in exactly how they stress-test affordability — but the underlying duty to check you can cope with future rate rises was not removed. In practice this means the stress margin a lender applies today varies by lender and isn’t a single published figure, which is one reason your real maximum can differ noticeably from a simple income-multiple estimate like this one.

Deposit

How much deposit do you need?

You’ll usually need at least a 5% deposit to get a mortgage at all. 10% deposits are common and typically unlock better rates than a 5% deal, and 15%+ usually widens your choice of mortgages further and can improve the rate again. Note that the deposit people actually put down is often much higher than the minimum required — regional house-price differences (especially London) push the typical first-time-buyer deposit well above 5–10% in practice.

Beyond the multiple

Why two people on the same salary can be offered different amounts

A simple income-multiple estimate — like the one above — only shows a rough ceiling. Your real maximum depends on a full affordability assessment covering your existing debts and credit commitments, monthly outgoings, number of dependants, credit history, and type of employment (permanent vs fixed-term or self-employed income is often assessed differently). Two people earning exactly the same salary can be offered very different amounts once these are factored in.

Questions

Common questions