Education
Affordability Myths Debunked
Stop believing the 4.5× salary rule and calculator misconceptions. Learn what lenders actually test for and how affordability really works.
~8 min read
Last updated August 2026
Myth 1: "You Can Borrow 4.5× Your Salary"
❌ The Myth
"If I earn £50k, I can borrow £225k (4.5×). So I can afford a house up to about £270k with a deposit."
- This seems simple and widely known
- You hear it everywhere: from friends, online forums, property websites
- It gives a quick answer without needing a calculator
✓ The Reality
4.5× is ONE test, not the only test. Lenders run TWO tests simultaneously:
- LTI (Loan-to-Income): Max 4–4.5× salary
- LTV (Loan-to-Value): Max 75–95% depending on deposit
Both must pass. If either fails, you're rejected.
Real example: You earn £50k and want to buy a £350k house. You have £35k deposit (10%).
- LTI check: Loan £315k ÷ £50k salary = 6.3×. FAIL (exceeds 4.5×)
- LTV check: LTV 90%. PASS (within limits)
Lender says NO because LTI failed, even though LTV is fine.
Myth 2: "If the Calculator Says Yes, the Bank Will Approve Me"
❌ The Myth
"This calculator shows I can afford a £400k house. So I'll just apply to the bank and get approved, right?"
- This calculator shows payment affordability (can you pay £X/month?)
- But lenders don't just check if you can pay the monthly amount
- They assume the calculator = pre-approval
✓ The Reality
Lenders test 20+ factors beyond just monthly payment:
- Credit score: Below 620 = rejected by most lenders
- Employment history: Less than 2 years in job = risk
- Existing debt: Car finance, student loans, credit cards all count against you
- Total debt-to-income: If you owe £500/month on other debts + £1,500 mortgage = lenders see £2,000/month obligations
- Savings/emergency fund: Do you have 3–6 months of expenses saved?
- LTI and LTV: (already mentioned above)
Real example: Calculator shows you can afford £1,500/month mortgage on a £300k house. But:
- You have £500/month car finance (3 years remaining)
- You have £200/month student loan debt
- Total obligations = £2,200/month
- Lender says: "Your total debt servicing is too high. REJECTED."
Myth 3: "Interest Rates Are the Only Thing That Changes Affordability"
❌ The Myth
"I'll just wait for rates to drop 0.5%, then I can afford a bigger house. Everything else stays the same."
- Rates do affect affordability (higher rates = higher payment)
- So it's easy to assume that rates are the main lever
✓ The Reality
Three levers matter equally:
- Interest rate: A 0.5% drop saves ~£50/month on a £250k loan
- Deposit size: Jump from 10% to 20% deposit = lower LTV (better rates) + lower monthly payment
- Mortgage term: Extend from 25 to 30 years = saves ~£80/month on same loan
Real example showing all three matter equally:
Starting scenario: £250k loan, 25-year term, 4.5% rate = £1,294/month
- Drop rate 0.5%: 4.0% rate = £1,194/month (save £100)
- Extend term 5 years: 30-year term = £1,215/month (save £79)
- Increase deposit 5%: Lowers loan to £237.5k = £1,229/month (save £65)
All three changes have similar impact. Don't wait only for rates to drop—consider saving more deposit or lengthening your term.
Myth 4: "Your Calculator Should Match My Bank's Numbers Exactly"
❌ The Myth
"My calculator shows £1,400/month, but my bank says £1,380/month. Your calculator is wrong."
- It's reasonable to expect exact numbers
- Small differences feel like errors
✓ The Reality
Different calculators use different assumptions:
- This calculator: Pure interest + principal on a standard amortizing mortgage. No insurance, no fees, no tax adjustments.
- Bank's calculator: Includes mortgage protection insurance, valuation fees, arrangement fees, possibly tax breaks (first-time buyer relief).
- Broker's calculator: May use different interest calculation methods (daily vs. monthly compounding).
Small differences (£20–50/month) are normal. Large differences (£200+) suggest different assumptions. Use this calculator to estimate; use your bank's for the exact figure before signing.