- Lenders typically approve 4–4.5× your income — but that's the ceiling, not the target.
- Housing costs above 28% of gross income is a common warning threshold; total debt payments above 35–40% of take-home puts most budgets under real strain.
- The full cost of owning goes well beyond the monthly payment — upfront fees, maintenance, running costs, and interest rate risk are all routinely underestimated.
- The right mortgage is the one that leaves you comfortable, not just solvent. For most buyers, that sits 15–30% below the lender's maximum.
What lenders actually look at
UK lenders use two main calculations when deciding what to lend you.
Income multiples. Most lenders will offer somewhere between 4 and 4.5 times your annual income, with some going up to 5× or even 5.5× for higher earners or certain professions. For a household income of £60,000, that's typically a maximum loan of £240,000–£270,000.
Affordability assessment. This looks at your actual monthly income and outgoings — committed credit payments, childcare, basic living costs — and stress-tests whether you could still afford the mortgage if interest rates rose. The Bank of England's previous "3% above reversion rate" stress test was relaxed in 2022, but lenders still apply their own.
The lender's job is to make sure you'll pay them back, even in difficult circumstances. They're not trying to figure out whether the mortgage will leave you with enough left over to live the life you want — that part is on you.
The gap between "approved" and "affordable"
Here's where a lot of first-time buyers and movers come unstuck. Imagine a couple earning £80,000 combined, approved for a £360,000 mortgage. On a 5% rate over 25 years, that's around £2,100 a month in repayments.
That £2,100 has to come out of a take-home pay of roughly £5,200 a month. That leaves £3,100 for everything else: council tax, utilities, food, transport, childcare if applicable, insurance, savings, pension contributions, and any sort of social life. In many parts of the UK, especially with children, that's tight to the point of unworkable.
The same couple borrowing £280,000 instead would pay roughly £1,640 a month — £460 less. Over a year that's £5,500 of breathing room, which is a meaningfully different quality of life. The smaller house, in most cases, doesn't feel £5,500 a year worse to live in.
A more useful rule of thumb
The lender's view of affordability is based on what's mathematically survivable. A more useful question is: what monthly mortgage payment leaves me comfortable, not just solvent?
A few rough guides commonly used:
- The 28% rule: housing costs (mortgage + insurance + council tax) shouldn't exceed 28% of gross income.
- The 35–40% rule: total debt payments (mortgage + any loans + credit minimums) shouldn't exceed 35–40% of gross income.
- The 50/30/20 budget check: 50% of take-home on needs (including mortgage), 30% on wants, 20% on savings and debt repayment. If the mortgage alone eats most of your "needs" 50%, the rest of the budget gets squeezed hard.
These are heuristics, not laws. A couple with no children, no commute costs, and stable jobs can comfortably push higher percentages than a family with two kids in nursery and one income that could disappear.
Enter your income, outgoings, and a target comfort level to get a figure that reflects what you can afford — not just what a lender will approve.
The four costs people underestimate
When people work out what they can afford, they usually focus on the monthly mortgage payment. But the real cost of owning a home is significantly broader.
1. Upfront fees
Beyond the deposit, you'll typically need:
- Stamp duty (for properties above the relevant threshold — currently £125,000 for movers and £300,000 for first-time buyers in England)
- Legal fees: typically £1,000–£2,000
- Survey: £400–£1,500 depending on type
- Mortgage product/arrangement fees: often £500–£2,000, sometimes addable to the loan
- Removals: £500–£2,000
For a £300,000 first-time-buyer purchase, you're looking at perhaps £3,000–£5,000 in upfront costs on top of the deposit. For a £500,000 second-time mover, it can easily be £20,000 once stamp duty is included.
2. Running costs
Owning costs more than renting per square foot, every month, before any mortgage interest:
- Buildings insurance: typically £15–£40/month
- Service charge and ground rent (for leasehold): can be anywhere from £50 to several hundred pounds per month
- Council tax: varies widely by band and area, often £150–£300/month
- Higher utility bills: most houses cost more to heat than most flats
- Maintenance: rough rule of thumb is 1% of property value per year, averaged over decades
That last one is the most under-budgeted. A boiler costs £2,000–£4,000 to replace. A roof can be £5,000–£15,000. You won't pay these every year, but you will pay them — and the maths over a 25-year ownership horizon works out at thousands per year on average.
3. The interest rate risk
When you take out a fixed-rate mortgage, you're locked into that rate for two, three, or five years — but the loan itself usually runs for 25 years or more. When your fix ends, you have to remortgage at whatever rates exist then.
If you stretched to afford the mortgage at 4.5%, and rates have moved to 6% by the time your fix ends, your monthly payment will jump. A £250,000 mortgage over 25 years costs £1,390/month at 4.5% but £1,610/month at 6% — an extra £220/month that has to come from somewhere. Building some headroom into your initial budget protects against this.
4. Life changes
Most mortgages last decades. The job you have now might not be the job you have in five years. You might want children, or already have them and find childcare costs higher than expected. You might want one partner to drop hours, take a sabbatical, or start a business. The further your monthly mortgage sits from the absolute maximum you can afford, the more room you have to adapt.
A practical framework
Here's a rough order of operations for getting to a sensible mortgage figure.
Start with your monthly take-home pay, not gross. That's the number you actually live on.
Subtract your essential non-housing costs — childcare, transport, food at a realistic level, utilities, insurance, debt payments, regular savings. Be honest, not optimistic.
What's left is your housing budget. Subtract council tax and an estimate of buildings insurance and maintenance, and what remains is what you can comfortably spend on the mortgage payment itself.
Convert that monthly mortgage payment back into a loan amount at the rates currently on offer. The mortgage affordability calculator does this directly.
Add your deposit to get the property price you should be looking at.
This number is almost always smaller than what the lender will offer you. That gap is the safety margin — and it's the difference between owning a home that improves your life and owning one that quietly dominates it.
Stretching is sometimes the right call
None of this is to say you should always go in below maximum. Stretching makes sense in specific situations:
- Early in your career, when income growth is likely
- In high-growth-potential areas, where the property itself is part of the long-term plan
- When the alternative is renting indefinitely at not-much-less per month
- When the property choice has a meaningful quality-of-life upgrade that you'd struggle to achieve later
The point isn't to never stretch — it's to stretch deliberately, with eyes open, rather than because the lender said you could.
The bottom line
The right mortgage isn't the biggest one you can get approved for. It's the one that lets you live the life you want around it. For most people, that number sits 15–30% below the lender's maximum, depending on circumstances.
Use your actual income and outgoings — not aspirational ones. The lender's letter tells you what's possible; your own budget tells you what's wise.
This article is for general information only and isn't personal financial advice. Mortgage rates and rules change frequently — figures used are for illustration only.