# What is debt-to-income ratio?

> Quick answer · Last updated 23 June 2026

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## In short

Debt-to-income (DTI) ratio is the percentage of your gross monthly income that goes on debt repayments — including the mortgage you are applying for. UK lenders use it alongside stress-tested affordability checks; there is no single official cap, but many lenders look for committed debt below roughly 40–45% of income.

When you apply for a mortgage, lenders calculate how much of your before-tax income is already swallowed by credit commitments: existing mortgages, loans, credit card minimum payments, car finance, child maintenance and sometimes BNPL. They add the proposed new mortgage payment and compare the total to your gross income.

There is no universal UK rule like the US '43% DTI limit'. Instead, FCA affordability rules require lenders to assess whether you could keep up repayments if rates rise or circumstances change. Most high-street lenders apply internal DTI or 'committed expenditure' caps — often in the 40–45% range for gross income, stricter for interest-only or buy-to-let.

Lowering your DTI before applying can increase borrowing power. Pay down credit cards, clear or reduce car finance, cancel unused BNPL plans, and avoid new credit in the months before application. Lenders use credit file data and your declared outgoings, so inconsistencies can delay or decline an offer.

DTI is only one part of affordability. Deposit size, loan-to-value, employment type, age at end of mortgage term and dependent costs all matter. Use a mortgage calculator for repayments, then add other debts to see your own ratio — if it is above 40%, reducing debts or increasing income may be necessary before remortgaging or buying.

## Related

- [Mortgage stress test](https://moneyguide.org.uk/answers/what-is-the-mortgage-stress-test/)
- [What is loan-to-value (LTV)?](https://moneyguide.org.uk/answers/what-is-loan-to-value-ltv/)
- [Mortgage calculator](https://moneyguide.org.uk/tools/mortgage-repayment-calculator/)

## Primary source

gov.uk/buying-a-home/preparing-to-buy

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Independent UK money guidance from [Money Guide](https://moneyguide.org.uk). Information only — not regulated financial advice.