Reviewed by Mustafa Bilgic
Founder, WebCalculator
DTI tiers reflect general UK lending practice. Individual lender criteria vary. Not financial or mortgage advice — speak to a qualified broker.
The debt-to-income ratio calculator shows how UK mortgage lenders will assess your borrowing capacity. Enter your gross monthly income and total monthly debt payments to see your DTI percentage and which tier of lenders are likely to approve you.
Monthly income vs monthly debts
Your debt-to-income ratio is a simple percentage: total monthly debt payments divided by gross monthly income.
For example, if you earn £3,500 a month gross and your debts total £800, your DTI is 22.9% — comfortably in the "wide lender choice" tier.
Do not include: council tax, utility bills, food, insurance premiums or subscriptions. These are living costs, not debt obligations.
The mortgage affordability calculator shows how much you could borrow. The mortgage calculator works out monthly repayments. For overall pay, try the salary calculator.
Most UK lenders prefer a DTI below 40%. Under 30% gives you the widest choice of lenders and rates. Between 30% and 40% most mainstream lenders will still consider you. Above 40% you may need a specialist broker, and above 50% very few lenders will approve.
Add up all your monthly debt payments — mortgage or rent, credit cards, loans, car finance, child maintenance — and divide by your gross monthly income. Multiply by 100 to get a percentage. For example, £1,200 debts on £4,000 income = 30%.
UK mortgage lenders typically use gross income (before tax) when calculating your debt-to-income ratio. This is different from personal budgeting, where net income is more relevant.
Include your existing mortgage or rent, personal loans, credit card minimum payments, car finance, student loan payments, child maintenance and any other regular debt obligations. Do not include household bills like utilities, council tax, food or insurance.
It is very difficult. A DTI above 50% means more than half your gross income goes to debt. Most mainstream lenders will decline, but some specialist lenders may consider you — typically at higher interest rates. Reducing debts before applying will improve your options.
Yes. Lenders calculate your DTI including the proposed new mortgage payment, not just existing debts. This is called the back-end DTI. The calculator lets you include your expected mortgage to see the full picture.