Mortgage Affordability Calculator UK
Estimate how much a UK lender will let you borrow based on your income, your partner’s income, and your monthly commitments — before you start house-hunting.
There are two completely different mortgage questions, and most people confuse them. The first is “what will it cost me?” — that’s the Mortgage Calculator. The second is “what will a lender actually give me?” — and that’s this one. Affordability is the ceiling on your house search, and it’s set by a formula most buyers never see: an income multiple, a stress test against a higher interest rate, and a deduction for everything you already owe. Get a realistic figure here and you’ll house-hunt in the right bracket instead of falling for something a lender will quietly decline. The number this gives is an estimate — your actual offer depends on the lender’s own affordability model, your credit file, and the deposit you bring.
Income details
Deposit and savings
Monthly affordability
Monthly commitments
Affordability estimate
Estimated maximum property price
Calculating…
Calculating…
Maximum mortgage
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Usable deposit
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Estimated monthly payment
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Payment / gross income
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Income multiple used
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Affordability status
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How much you could borrow — quick lookup
Two ready-reckoners based on the income multiples UK lenders typically use. The left table shows borrowing for a single applicant at multiples of 4, 4.5, and 5 times income; the right shows joint applications, where lenders use combined income. These are starting points — your real figure is reduced by monthly commitments and capped by the stress test, both covered below.
| Income | ×4 | ×4.5 | ×5 |
|---|---|---|---|
| £25k | £100k | £113k | £125k |
| £30k | £120k | £135k | £150k |
| £40k | £160k | £180k | £200k |
| £50k | £200k | £225k | £250k |
| £60k | £240k | £270k | £300k |
| £75k | £300k | £338k | £375k |
| £100k | £400k | £450k | £500k |
| Incomes | Combined | Borrow |
|---|---|---|
| £30k + £25k | £55k | £248k |
| £35k + £35k | £70k | £315k |
| £40k + £30k | £70k | £315k |
| £50k + £35k | £85k | £383k |
| £60k + £40k | £100k | £450k |
| £80k + £50k | £130k | £585k |
Notice the two £70k rows in the joint table reach the same £315k, whether it’s split £40k/£30k or evenly £35k/£35k — lenders care about the total, not the split. But that’s before commitments. The same couple with a £250-a-month car loan would see their ceiling drop by roughly £45,000, because affordability isn’t just about what you earn — it’s about what’s left after what you already owe.
How mortgage affordability works in the UK
Borrowing capacity is decided in three stages, and most people only know about the first. A lender starts with an income multiple to set a rough ceiling, then runs an affordability assessment that deducts your real outgoings, then applies a stress test to confirm you could survive a rate rise. The lowest of those three results is what you’re offered. Understanding all three is the difference between knowing your number and being surprised at the application stage.
Stage one: the income multiple
The multiple is a blunt first cut. Most UK lenders centre on 4.5 times income, stretching to 5 or even 5.5 for higher earners, certain professions (doctors, solicitors, accountants), or government-backed schemes. A nurse and a teacher earning £35,000 each have a combined £70,000, so a 4.5× lender would start them at around £315,000. The catch is that this number is a maximum the lender will *consider*, not an amount they’ll necessarily approve.
Stage two: the affordability assessment
This is where the headline multiple meets reality. The lender looks at your actual monthly income against your actual monthly commitments — car finance, personal loans, credit card minimums, childcare, school fees, existing maintenance payments — and works out how much you have left to service a mortgage. Every £100 a month of existing debt removes roughly £18,000 of borrowing capacity, because that’s £100 a month that can’t go toward a mortgage payment. A £250-a-month car finance agreement quietly costs you around £45,000 of the house you can buy. This is the single biggest reason real offers come in below the income-multiple figure, and the one people are most shocked by.
Stage three: the stress test
UK lenders are required to check that you could still afford the mortgage if interest rates rose well above the rate you’re offered. They model your payment at a notional higher rate — often several points above the deal rate — and confirm it still fits your budget. This is why a mortgage that looks comfortably affordable at today’s rate can still be declined: the lender isn’t testing today’s payment, it’s testing a hypothetical stressed one. A £225,000 loan that costs around £1,251 a month at 4.5% might be stress-tested at 8%, where it would cost £1,737 — and if your budget doesn’t clear that higher figure, the loan shrinks. The FCA sets the framework lenders work within here.
Where the deposit fits in
Your deposit doesn’t increase how much you can borrow — that’s set by income and affordability — but it determines the loan-to-value (LTV) band you fall into, which sets your rate. A bigger deposit means a lower LTV, a cheaper rate, and a lower monthly payment, which in turn makes the affordability assessment easier to pass. So while the deposit isn’t part of the borrowing calculation directly, it loosens the affordability constraint by reducing the payment you need to service. On a £300,000 home, moving from a 5% deposit (95% LTV) to a 15% deposit (85% LTV) can shift you into a materially cheaper rate tier.
Four worked examples
Realistic affordability outcomes showing how the three stages interact — and why the final figure rarely matches the income multiple alone.
Example 1 — Leila (single, no debts)
£40,000 salary, clean finances, £25k deposit
Monthly debts: £0 · Affordability: no reduction
Stress test: passes comfortably
Likely borrowing: ~£180,000 · Budget with deposit: ~£205,000
Leila is the textbook clean case. No car finance, no loans, no credit card balances, so the affordability assessment doesn’t claw anything back from the income multiple. Her £180,000 ceiling holds, and with her £25,000 deposit she’s house-hunting around £205,000. Clean finances are worth real money at the application stage — the absence of debt is itself a borrowing asset.
Example 2 — Marcus & Jen (joint, car finance)
£70,000 combined, £250/mo car loan
Car finance £250/mo reduces capacity by ~£45,000
Adjusted borrowing: ~£270,000
On paper Marcus and Jen can borrow £315,000. In practice, their £250-a-month car finance pulls roughly £45,000 off that, landing them nearer £270,000. The lender treats that £250 as money permanently unavailable for a mortgage payment, so it shrinks the loan accordingly.
The lesson many couples learn too late: clearing or settling a car finance agreement before applying can recover tens of thousands of borrowing power. If the car loan has only a few months left, lenders sometimes ignore it — worth asking before you commit to settling early.
Example 3 — Priya (high earner, professional multiple)
£100,000 salary, eligible for 5× lending
Professional 5×: £100,000 × 5 = £500,000
Difference from the higher multiple: £50,000
Priya qualifies for an enhanced income multiple — some lenders offer 5× or more to higher earners and certain professions. That single difference, 4.5× versus 5×, is worth £50,000 of borrowing on her income. It’s why higher earners benefit from a broker who knows which lenders stretch multiples, rather than walking into the first high-street bank.
The trade-off: borrowing at 5× income leaves less monthly headroom, so the stress test bites harder. Just because a lender will offer it doesn’t mean the repayment is comfortable — borrowing the maximum is rarely the same as borrowing the sensible amount.
Example 4 — The Osei family (debts and childcare)
£85,000 combined, £500/mo total commitments
£500/mo commitments reduce capacity by ~£90,000
Adjusted borrowing: ~£292,000
The Oseis earn well, but childcare, a personal loan, and credit card payments add up to £500 a month of fixed outgoings. That strips around £90,000 from their income-multiple ceiling, dropping them from £382,500 to roughly £292,000. Childcare is the quiet affordability killer for families — it’s a large, fixed, monthly cost that lenders treat exactly like debt.
There’s a timing angle here too: as children start school and childcare costs fall, borrowing capacity recovers. Families sometimes find their affordability improves significantly within a year or two, which can be worth waiting for if they’re close to the property they want.
The three tests every lender runs
A mortgage offer isn’t a single calculation — it’s three separate hurdles, and your final figure is the lowest of the three. Most applicants only know about the first and get blindsided by the other two. Understanding all three lets you walk into an application knowing your real number, not the optimistic one. Here’s what the lender actually checks, in order:
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1
The income multiple — the ceiling
Your income times a multiple, usually around 4.5×, sets the absolute maximum the lender will consider. Joint applications use combined income. This is the only test most people know about, and it’s the most generous of the three.
It’s a ceiling, not a target. Nothing below this point is guaranteed — the next two tests can pull the figure down sharply.
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2
The affordability assessment — the deductions
The lender subtracts your real monthly commitments — car finance, loans, credit cards, childcare — to see what’s genuinely left for a mortgage. Every £100/month of debt removes around £18,000 of capacity.
This is where the income-multiple ceiling meets your actual life. It’s the test that most often surprises applicants, because it converts everyday outgoings into lost borrowing.
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3
The stress test — the safety margin
The lender checks you could still pay if rates rose well above the offered rate, modelling the payment at a notional higher rate. If your budget doesn’t clear the stressed payment, the loan shrinks until it does.
This is why a loan affordable at today’s rate can still be declined — the test isn’t today’s payment, it’s a hypothetical worse one. It protects you as much as the lender.
The three tests on one £70k household with a £250 car loan
Watch the number fall at each stage:
The gap between the income-multiple headline and the real offer — £315,000 down to £255,000 in this case — is £60,000. That’s the difference between the house you think you can afford and the one a lender will actually fund. People who only know about the first test go house-hunting with the wrong budget and have offers fall through; people who know all three walk in with a realistic number and a stronger position.
Why the income multiple alone misleads you
Property portals and casual advice almost always quote the income-multiple figure, because it’s simple and flattering. “You earn £70k between you, so you can borrow £315k” feels like solid information. But it ignores the two tests that come after, and those are precisely the ones that decide your real offer. Treating the multiple as your budget is how buyers end up making offers they can’t finance, then scrambling when the lender’s actual figure arrives lower.
The second trap is forgetting that affordability is dynamic. Pay off a car loan, and your capacity jumps. Take on a new credit agreement weeks before applying, and it drops. Lenders look at your commitments at the point of application, so the months before you apply are when small financial decisions have outsized effects on the house you can buy.
Two scenarios that change what you can borrow
What if…
You cleared a £250/mo car loan?
What if…
You stretched to the maximum?
Key affordability terms explained
Affordability has its own vocabulary, and lenders rarely explain it. The ten terms below cover what you’ll meet in a mortgage-in-principle, a broker conversation, and the questions an underwriter asks.
- Income multiple
- The number a lender multiplies your income by to set a maximum loan — usually around 4.5×, stretching to 5× or more for higher earners and certain professions. Joint applications use combined income. It sets the ceiling, not the offer; the affordability assessment and stress test can reduce it.
- Affordability assessment
- The lender’s review of your real income against your real outgoings — debts, childcare, regular commitments — to work out how much is genuinely available for a mortgage. This is where the income multiple meets your actual budget, and it’s the most common reason offers come in lower than expected.
- Stress test
- A regulatory check that you could still afford the mortgage if rates rose well above the offered rate. Lenders model the payment at a notional higher rate and confirm it still fits. A loan affordable today can be declined because it fails the stressed scenario.
- Debt-to-income ratio DTI
- The share of your gross income consumed by debt repayments. Lenders use it as a risk signal — a high DTI means less room to service a mortgage. As a rough guide, every £100/month of debt cuts borrowing by ~£18,000, because that £100 can’t go toward a mortgage payment.
- Loan-to-value LTV
- Your loan as a percentage of the property’s value, set by your deposit. A bigger deposit means lower LTV, a cheaper rate, and a lower payment — which makes the affordability assessment easier to pass. The deposit doesn’t raise your borrowing limit directly, but it loosens the affordability constraint.
- Mortgage in principle MIP / AIP / DIP
- A lender’s provisional indication of how much they’d lend, based on a soft credit check and the figures you give. Useful for house-hunting and making credible offers, but not a guarantee — the full application can still come back lower once documents and a hard credit check are in.
- Gross vs net income
- Lenders base the income multiple on gross (pre-tax) income, but the affordability assessment works from your net (take-home) figure, since that’s what actually pays the mortgage. Bonuses, commission, and self-employed income are often counted at a discount or averaged over two to three years.
- Committed expenditure
- Fixed, ongoing outgoings a lender treats like debt: car finance, loans, credit card minimums, childcare, maintenance, school fees. These are deducted in the affordability assessment. Discretionary spending (subscriptions, eating out) is assessed more loosely but can still affect the decision.
- Deposit
- The cash you put in up front, expressed as a percentage of the price. UK lenders typically require a minimum of 5%, though 10% or more unlocks better rates. The deposit plus your borrowing equals your property budget — and a larger deposit eases affordability by lowering the payment.
- Soft vs hard credit check
- A soft check (used for a mortgage in principle) doesn’t affect your credit score and isn’t visible to other lenders. A hard check (at full application) leaves a footprint. Several hard checks in a short window can dent your score, so it pays to be selective about full applications.
Five mistakes UK buyers make on affordability
These are the recurring errors brokers see and the threads that fill r/UKPersonalFinance. Each one quietly costs borrowing power or sinks an application that should have succeeded.
Treating the income multiple as your budget
“We earn £70k, so we can borrow £315k” ignores the two tests that follow. Existing debts and the stress test routinely pull the real offer £40,000–£60,000 lower. Buyers who house-hunt on the multiple alone make offers they can’t finance and watch them collapse at the application stage.
Cost: offers falling through Fix: budget on the realistic figure, not the ceilingTaking on new credit just before applying
A new car on finance, a phone contract, or a “buy now, pay later” balance weeks before a mortgage application can knock tens of thousands off your borrowing. Lenders assess commitments at the point of application, so the months before you apply are exactly when not to add fixed monthly costs.
Cost: £18k+ capacity per £100/mo added Fix: freeze new credit 3–6 months before applyingApplying to several lenders at full application
Each full application triggers a hard credit check, and several in a short window can lower your score — making the next lender warier. Use a mortgage in principle (soft check) to compare, or a broker who knows which lender fits before you commit to a hard search. Don’t scattergun full applications.
Cost: damaged credit score mid-search Fix: use soft-check MIPs and a broker to narrow downForgetting that bonuses and commission count less
If a chunk of your income is variable — bonus, commission, overtime — lenders often count it at a discount or not at all, and self-employed income is usually averaged over two to three years. A £60k base with a £20k bonus may be assessed nearer £66k, not £80k. Know which income a lender will actually use before you set your budget.
Cost: overestimating budget by £50k+ Fix: confirm how variable pay is treated upfrontBorrowing the maximum the lender offers
Just because a lender will approve your ceiling doesn’t mean you should take it. Borrowing the maximum leaves no cushion for a rate rise at remortgage — the very thing the stress test guards against. A two-point rise on a stretched loan can add hundreds a month when the fix ends. Borrowing below your limit is what makes the next deal survivable.
Cost: payment shock at remortgage Fix: borrow below your ceiling, keep headroomFrequently asked questions
How much can I borrow for a mortgage based on my salary?
As a starting point, UK lenders multiply your income by around 4 to 4.5, so a £40,000 salary supports roughly £160,000–£180,000, and a £70,000 joint income around £315,000. Some lenders stretch to 5× or more for higher earners and certain professions.
That’s the ceiling, not the offer. Your real figure is then reduced by monthly commitments (the affordability assessment) and capped by the stress test. Two people on the same salary can be offered very different amounts depending on their existing debts.
Why is my mortgage offer lower than my income multiple?
Because the income multiple is only the first of three tests. After it, the lender runs an affordability assessment that deducts your real monthly commitments — car finance, loans, credit cards, childcare — and a stress test that checks you could still pay at a much higher rate.
Every £100 a month of existing debt removes around £18,000 of borrowing capacity. A £250-a-month car loan can quietly cost you £45,000 of the house you can buy. The offer you receive is the lowest of the three test results, which is usually well below the headline multiple.
Do lenders use gross or net income for affordability?
Both, for different purposes. The income multiple uses gross (pre-tax) income to set the ceiling. The affordability assessment works from net (take-home) income, since that’s what actually pays the mortgage each month.
Variable income is treated cautiously: bonuses, commission, and overtime are often counted at a discount or averaged, and self-employed income is usually averaged over two to three years of accounts. A £60k base with a £20k bonus may be assessed nearer £66k rather than the full £80k.
Does my deposit affect how much I can borrow?
Not directly — how much you can borrow is set by income and affordability, not deposit size. But the deposit determines your loan-to-value band, which sets your rate, which sets your monthly payment. A bigger deposit means a cheaper rate and a lower payment, which makes the affordability assessment easier to pass.
So a larger deposit doesn’t raise your borrowing limit, but it loosens the affordability constraint and increases your total property budget (deposit plus loan). On a £300,000 home, moving from a 5% to a 15% deposit can shift you into a materially cheaper rate tier.
What is the mortgage stress test and why does it matter?
The stress test is a regulatory check that you could still afford your mortgage if interest rates rose well above the rate you’re offered. Lenders model the payment at a notional higher rate and confirm it still fits your budget.
It matters because a mortgage that’s comfortably affordable at today’s rate can still be declined if it fails the stressed scenario. A £225,000 loan costing around £1,251 a month at 4.5% might be tested at 8%, where it would cost £1,737 — and if your budget doesn’t clear that, the loan shrinks. The test protects you from over-borrowing as much as it protects the lender.
Should I clear my debts before applying for a mortgage?
Often yes — clearing a monthly commitment before you apply can recover significant borrowing power. Settling a £250-a-month car finance agreement can add roughly £45,000 to your ceiling, frequently more than the cost of settling it.
The exceptions: if a loan has only a few months left, some lenders will ignore it anyway, so settling early may not help. And don’t drain your deposit to clear debt — a smaller deposit pushes you into a higher LTV and a worse rate, which can offset the gain. It’s a balance worth modelling, or discussing with a broker, before acting.
Does a mortgage in principle guarantee I’ll get the loan?
No. A mortgage in principle (also called an agreement or decision in principle) is a provisional indication based on a soft credit check and the figures you provide. It’s useful for house-hunting and making credible offers, and estate agents often ask to see one.
But the full application can still come back lower or be declined once the lender verifies documents, runs a hard credit check, and values the property. Treat the figure as a strong guide, not a guarantee, and don’t commit to a purchase you can only finance at the very top of it.
How can I increase how much I’m able to borrow?
The most effective levers are reducing monthly commitments and improving your credit profile. Clearing debts directly increases capacity (around £18,000 per £100/month cleared). Avoiding new credit in the months before applying preserves it. A larger deposit lowers your payment and eases the affordability test.
Beyond that, a broker can match you to lenders with more generous multiples or treatment of variable income — the right lender for your profile can be worth tens of thousands. For impartial guidance on the whole process, MoneyHelper is a good independent starting point.
Related calculators
Knowing what you can borrow is the first step. These calculators handle what comes next — the cost, the tax, and the take-home that funds it all.
Methodology & sources
How the estimate works
The calculator applies an income multiple to your gross income (single or combined) to set a borrowing ceiling, then reduces it based on your monthly commitments, since every pound of fixed monthly debt removes borrowing capacity that would otherwise service a mortgage. A simplified stress-test adjustment reflects that lenders cap lending where the payment at a higher notional rate would exceed comfortable affordability.
The relationship between a monthly commitment and lost capacity is derived from standard amortisation maths: a given monthly amount supports a given loan size at typical rates and terms, so diverting it to debt removes that loan capacity. Figures are estimates to illustrate how the three stages interact, not a lending decision.
UK rules and conventions used
- Income multiple: typically 4–4.5×, up to 5×+ for higher earners (varies by lender)
- Joint applications: combined income × multiple
- Affordability: committed monthly outgoings deducted from capacity
- Capacity rule of thumb: ~£18,000 lost per £100/month of debt
- Stress test: payment modelled at a notional rate above the offered rate
- Income basis: gross for the multiple, net for affordability; variable pay discounted
- Deposit: minimum 5%; affects LTV and rate, not the borrowing limit directly