Example result based on the prefilled values.
Payment-Supported Loan
£466,817.30
Mortgage Payment Budget
£2,866.67
Continue your plan
Useful next calculations
Rates & sources
This is a user-assumption planning model, not lender underwriting. UK lenders assess income, spending, commitments, credit and future-rate affordability under their own policies.
Source: FCA — mortgage interest-rate stress guidance — check the linked guidance and any live quote before acting.
When to use this calculator
- Before comparing lenders, brokers, or repayment options.
- When you want to test how a different deposit, rate, or term changes affordability.
- When you need a quick estimate before using a formal quote or agreement in principle.
- When you are stress-testing your budget against a potential rate rise to see the impact on monthly payments.
- When you want to understand the full cost of borrowing — not just the monthly figure — before you commit.
Example: checking borrowing headroom before viewing homes
Use these sample inputs as a quick scenario test, then change one variable at a time to compare outcomes.
Annual household income
£52,500
Monthly fixed outgoings
£1,500
Monthly safety buffer
£500
Stress-tested mortgage rate
5.75%
Treat the maximum loan as an outer estimate. Re-run the calculation with higher monthly expenses and a higher interest rate, then compare the resulting payment with the amount you can sustain while still saving for repairs and other goals.
How to read your results
Payment-Supported Loan
Use this metric to compare scenarios side by side and understand how changes in the key inputs drive the final outcome. If the figure surprises you, isolate one variable at a time and rerun the calculation to identify which assumption is responsible.
Mortgage Payment Budget
Use this metric to compare scenarios side by side and understand how changes in the key inputs drive the final outcome. If the figure surprises you, isolate one variable at a time and rerun the calculation to identify which assumption is responsible.
Method & assumptionsAuthoritative sources
This planning calculator converts the monthly payment left after the spending and safety buffer you enter into a loan amount at the selected rate and term. It does not use a lender income multiple and does not replicate underwriting. The output is a payment-supported ceiling based solely on your assumptions, not an amount a lender has assessed as affordable.
Real lenders review income, debts, dependants, regular spending, credit history, loan-to-value and the effect of future rate rises under their own policies. Include all ongoing commitments and keep a realistic buffer rather than allocating every spare pound to a mortgage. Obtain a decision in principle from a regulated lender or mortgage adviser before relying on a borrowing figure.
Official references
Common mistakes
- !Mixing up loan amount and property value, which can distort affordability and LTV.
- !Using a headline rate but forgetting fees, insurance, taxes, or repayment type.
- !Testing only one term length instead of comparing the payment and total cost together.
- !Forgetting that a repayment mortgage and an interest-only mortgage produce very different monthly figures and total costs.
- !Not accounting for the impact of a rate revert after an introductory fixed period ends, which can sharply increase payments.
What to do next
- Repeat the estimate using a higher mortgage rate and all recurring credit commitments to create a cautious range.
- Turn the affordable loan into a monthly repayment using the mortgage calculator.
- Subtract the deposit, SDLT, conveyancing, survey, and moving costs from the cash available before setting a property budget.
Go deeper — 1 guide reference this calculator
Frequently asked
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