UK finance jargon - in plain English
A measure of how much of your monthly income goes toward repaying debt.
Your debt-to-income ratio (DTI) compares your total monthly debt repayments to your gross monthly income. It is calculated by dividing your total monthly debt payments by your gross monthly income and multiplying by 100. UK mortgage lenders typically assess affordability through income multiples and detailed affordability calculations rather than a single DTI figure. That said, the underlying idea is the same: lenders want to see that your total debt commitments are manageable relative to your income. A lower ratio of debt to income generally supports a stronger application.
Your gross monthly income is £3,500. You pay £300 on a car loan, £150 on a personal loan, and you are applying for a mortgage with payments of £900. Total monthly debt would be £1,350, giving a DTI of around 39%. Lenders use figures like this, alongside affordability stress tests, to decide what you can borrow.
DTI as a label is more common in the US. UK lenders tend to use income multiples and their own affordability models, but the principle of debt relative to income is central to any mortgage assessment. Your full financial picture matters more than any single number.
Last updated: June 2026. Sources: HMRC / GOV.UK / Student Finance England / FCA where relevant.
People focus on whether they can afford the monthly payment today and do not consider how their DTI looks on paper to a lender. A high DTI can result in a smaller mortgage offer even when you feel comfortable with the payments.