Budget-First Mortgage Calculator

How much could you borrow on your monthly budget?

Start with the monthly payment you’d actually feel comfortable making. We’ll work backwards to show the mortgage size that fits, then stress test it against a rate rise.

£
%
yrs
Repayment type
You could borrow up to
£0
Based on a £1,000 monthly payment at 4.5% over 25 years

Stress test: if your rate rose by 3%

%

What the same mortgage would cost at the higher rate, and how much extra you’d pay each month.

New monthly payment
£0
+£0 per month
Stressed rate used
0.0%
+£0 per year

Calculations use the standard repayment mortgage formula. Default stress test of 3 percentage points is in line with FCA affordability guidance. For illustration only. Actual lender offers depend on income, deposit, credit history and other factors.

Most mortgage calculators start by asking how much you earn. This budget-first calculator starts somewhere far more practical: what monthly payment would actually feel comfortable for you.

Instead of stretching yourself to the maximum a lender might offer, our budget-first mortgage calculator works backwards from your chosen monthly payment to estimate how much you could borrow. 

It then stress tests your mortgage against higher interest rates, so you can see how a rate rise could affect your repayments before you commit. That gives you a clearer picture of what’s realistically affordable for you. 

Whether you’re a first-time buyer, moving home, or simply planning ahead, this calculator can help you:

  • Estimate how much you could borrow based on your monthly budget
  • Compare repayment and interest-only mortgages
  • See how mortgage rates affect affordability
  • Stress test your repayments against future rate rises
  • Avoid overextending yourself financially.

Just enter the monthly payment you’d feel comfortable making, choose an interest rate and mortgage term, and we’ll do the maths for you.