UK Mortgage Affordability Calculator
How much can a UK household actually borrow? Enter gross household income, deposit, and any existing monthly debt, the calculator returns the maximum borrowing based on a lender stress test (typical quoted mortgage rate + 1 percentage point = 5.81% currently) and the standard 4.5× loan-to-income ceiling. The lower of the two is the binding constraint. Income is a figure you enter yourself; this site does not load real income data. Runs entirely in your browser, no data is sent to a server.
Affordability inputs
How the affordability rules work
UK mortgage affordability is governed by two binding constraints. The first is the loan-to-income (LTI) cap: under FCA flow limits, no more than 15% of a lender's new mortgages can be at LTI above 4.5×, which in practice means most borrowers are capped at 4.5× their gross household income. Higher-income households can sometimes stretch to 5×, but only at a few specialist lenders.
The second is the lender stress test: the borrower must be able to afford the monthly payment if the interest rate rose to the contract/quoted rate plus 1 percentage point (currently 5.81%, based on the average 75% LTV 2-year fix). The FCA withdrew its prescribed stress-test requirement (the historical contract-or-reversion-rate + 3 rule, MCOB 11.6.18R) in 2022, and lenders now set their own stress, typically around the offered rate plus 1 percentage point. Total monthly debt service (mortgage + existing debt) must fit within roughly 35% of net household income for a comfortable outcome.
The binding ceiling is the lower of the two constraints. For most borrowers, the LTI cap binds, meaning a higher income unlocks more borrowing in a 1-to-4.5 ratio. For high-cost-of-living regions or high-debt borrowers, the stress test binds, meaning paying down credit-card debt or shortening the term has the larger effect on the borrowing ceiling.
Worked affordability scenarios
Five representative UK household scenarios with the maximum borrowing, target property price, and stress-test outcome computed at the current Bank Rate plus a typical product margin.
First-time buyer on £50k in London
- Income:
- £50,000/yr
- Deposit:
- £30,000
- Target price:
- £285,000
- Term:
- 30 years
- Rate:
- 4.81%
- Monthly:
- £1,339
- Band:
- stretched
Remortgaging £200k at the end of a 2-year fix
- Income:
- £70,000/yr
- Deposit:
- £100,000
- Target price:
- £300,000
- Term:
- 22 years
- Rate:
- 4.81%
- Monthly:
- £1,229
- Band:
- comfortable
Buy-to-let investor in Leeds
- Income:
- £75,000/yr
- Deposit:
- £65,000
- Target price:
- £175,000
- Term:
- 25 years
- Rate:
- 5.31%
- Monthly:
- £663
- Band:
- comfortable
Couple earning £90k in Manchester
- Income:
- £90,000/yr
- Deposit:
- £45,000
- Target price:
- £320,000
- Term:
- 25 years
- Rate:
- 4.65%
- Monthly:
- £1,552
- Band:
- comfortable
High earner on £150k in Cambridge
- Income:
- £150,000/yr
- Deposit:
- £100,000
- Target price:
- £525,000
- Term:
- 25 years
- Rate:
- 4.65%
- Monthly:
- £2,399
- Band:
- comfortable
Affordability questions
Why does the calculator stress at base + 1 percentage point?
Until 2022, the FCA required UK lenders to stress at the higher of the contract rate or the lender's reversion rate plus 3 percentage points (MCOB 11.6.18R). In August 2022 the FCA removed the specific 3% stress requirement, leaving lenders to set an appropriate stress at their own discretion. Most lenders settled on the contract/quoted rate plus 1 percentage point at the time of the offer, which is what this calculator uses (based on the average 75% LTV 2-year fix). A more conservative borrower or a lender with stricter standards may prefer contract rate + 2.
Why is the LTI cap usually 4.5× and not 5×?
Under FCA flow limits, no more than 15% of a UK lender's new mortgages in any reporting period can be at LTI above 4.5×. That is a flow limit on the lender, not a hard cap on the borrower, so individual borrowers can secure 5× deals at lenders who have headroom in their flow allocation, but only roughly one in seven applications go through at that level. For planning, 4.5× is the realistic ceiling.
How does paying down credit-card debt affect borrowing?
The stress test counts total monthly debt service (mortgage + credit cards + car finance + personal loans) against net income. A £200/month credit-card commitment typically reduces the borrowing ceiling by £30,000–£40,000 on a 25-year term at current rates. For borrowers near the limit, paying down debt before applying is one of the highest-return moves available, a £200/month reduction effectively unlocks the equivalent of a £40,000 income uplift.
Does the calculator handle joint applications?
Yes, the "gross household income" input takes the combined gross income of all named applicants. Lenders typically pool incomes for the LTI calculation up to two named applicants. For applications with three or more applicants, individual lenders vary; the income cap typically uses the highest two earners plus a partial credit for the third.
Where can I see the underlying maths?
The LTI cap is documented in the FCA's flow-limit guidance; the stress-test methodology is documented in MCOB 11.6 (post-2022 revision). Both are cited in full on the methodology page.
Related resources
According to the Bank of England and HM Land Registry, whose House Price Index is compiled from more than 1,000,000 registered property transactions a year, the figures referenced on this page draw on the June 2026 Bank of England quoted-rate snapshot and the April 2026 House Price Index release under the Open Government Licence. Our methodology records each series and refresh cadence.