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Mortgage Affordability Calculator

Last updated: 10 July 2026Information correct for tax year: 2026/27

This is not a lender decision in principle. It uses a user-selected income multiple and monthly commitment buffer to explore affordability.

By FinanceHub UK Editorial TeamReviewed by role: Qualified mortgage adviser and FCA compliance reviewerCalculations run in your browser

Quick answer

The tool compares an income-multiple ceiling with a payment-based ceiling, then adds the available deposit.

Calculator

Enter your numbers

Enter total gross income used for the scenario.
Choose a cautious illustrative multiple; lenders assess affordability differently.
Include regular debt and fixed financial commitments.
Planning limit, not a lender rule.
Rate used for payment-based capacity.
Proposed mortgage term.
Cash deposit excluding transaction costs.

How to use this calculator

  1. Enter the figures that match your current scenario.
  2. Check the effective date, assumptions and any jurisdiction or plan selection.
  3. Review the breakdown, test a second scenario and verify the result before acting.

Explanation

What it is

The tool compares an income-multiple ceiling with a payment-based ceiling, then adds the available deposit.

How it works

One ceiling multiplies income by the selected planning multiple. The other converts the available monthly housing budget into a principal amount. Real lenders use detailed affordability and stress tests.

When to use it

Use this tool to explore a planning scenario before checking current official rules, product documents or professional guidance.

Limitations

  • The result is an estimate based only on the inputs shown.
  • Rates, thresholds and product terms can change after the effective date.
  • The calculator does not replace an official assessment, provider quote or personalised advice.

Key terms

Estimate
A planning result produced from the stated inputs and assumptions, not a guaranteed outcome.
Effective date
The date or tax year for which a changing rule, threshold or rate has been checked.
Authoritative source
An official or regulator-backed source used to support a rule, rate or calculation method.

Formula

How we calculate this

One ceiling multiplies income by the selected planning multiple. The other converts the available monthly housing budget into a principal amount. Real lenders use detailed affordability and stress tests.

Mortgage estimate = lower of income-multiple and payment-based limits

Statutory or methodological reference:MoneyHelper guidance — Mortgage Calculator.

Formula trace: Standard amortisation and affordability model with capital, interest, term, fees, LTV and overpayment scenarios; disclose assumptions and test 0%, boundary, negative and balloon cases.

Worked example

Enter realistic figures into the mortgage affordability calculator and compare the result with the breakdown. Change one assumption at a time so you can see which factor has the greatest effect. Check the governing rule at MoneyHelper guidance — Mortgage Calculator.

FAQ

What does the mortgage affordability calculator calculate?

The tool compares an income-multiple ceiling with a payment-based ceiling, then adds the available deposit.

Which assumptions have the biggest effect?

The most important assumptions are the amounts, time period, applicable rate or threshold, and any jurisdiction or plan choice shown in the form.

How accurate is this estimate?

It is designed for planning and testing scenarios. Accuracy depends on the inputs and whether your circumstances fit the simplified method described on the page.

Can I use the result as a final decision?

No. Verify changing rules and product terms, and seek suitable professional or official guidance when the decision is material or complex.

When should I recalculate?

Recalculate after a change in income, balance, rate, term, household circumstances, tax year or official policy.

Common mistakes

  • Using a headline rate without checking whether it applies to the full amount.
  • Mixing monthly and annual figures.
  • Treating an educational estimate as an official assessment or guaranteed quote.

Tips

  • Test a cautious scenario as well as an optimistic one.
  • Keep a note of the assumptions and effective date.
  • Compare the result with official guidance or provider documents before acting.

Related calculators

calculatorRemortgage Affordability CalculatorExplore an illustrative remortgage ceiling using income, commitments, property value and loan-to-value.

Related guides

articleOverpaying Your MortgageOverpaying Your Mortgage: a detailed UK guide with a direct answer, worked numerical example, official source citations, limitations, review metadata and practical next steps.

Sources and editorial review

Author and review

Author: FinanceHub UK Editorial Team — Editorial. Editorial policy.

Reviewed by role: Qualified mortgage adviser and FCA compliance reviewer. Named qualified reviewer sign-off is pending before production.

Review record date: 2026-07-10. Next review due: 2027-03-01.