Your debt-to-income ratio (DTI) is one of the most important numbers in personal finance. Lenders use it to decide whether to approve your mortgage, car loan, or credit application — and on what terms.
What Is Debt-to-Income Ratio?
DTI compares how much you owe each month (debt payments) to how much you earn (gross monthly income).
DTI = (Total monthly debt payments / Gross monthly income) × 100
Example:
- Monthly debt payments: £1,200 (mortgage, car loan, credit card minimum)
- Gross monthly income: £4,000
DTI = (£1,200 / £4,000) × 100 = 30%
What Counts as Debt?
Include these monthly payments:
- Mortgage or rent
- Car loans
- Student loans
- Personal loans
- Credit card minimum payments
- Any other loan repayments
Do not include:
- Utilities (electricity, gas, water)
- Mobile phone bills
- Groceries and food
- Insurance premiums
- Subscriptions and entertainment
Front-End vs Back-End DTI
Mortgage lenders typically calculate two DTI ratios:
Front-end DTI (housing ratio): Only housing costs.
Front-end DTI = Monthly housing costs / Gross monthly income × 100
Housing costs include: mortgage payment (principal + interest), property taxes, home insurance, HOA fees.
Back-end DTI (total DTI): All monthly debt payments.
Back-end DTI = All monthly debt payments / Gross monthly income × 100
When lenders say "your DTI," they usually mean back-end DTI.
What DTI Do Lenders Want?
| DTI Range | Assessment | Mortgage eligibility |
|---|---|---|
| Below 20% | Excellent | Easy approval, best rates |
| 20–29% | Good | Strong position |
| 30–36% | Acceptable | Generally approved |
| 37–43% | Caution zone | May be approved with strong credit |
| 44–50% | High | Difficult to get conventional mortgages |
| Above 50% | Very high | Most lenders won't approve |
UK mortgage rule of thumb: Most lenders want back-end DTI below 40–45%. Some FCA-regulated lenders have stricter requirements.
US conventional mortgages: Fannie Mae and Freddie Mac typically require back-end DTI of 45% or below (sometimes 50% with compensating factors).
Worked Example: Should You Apply for a Mortgage?
Your situation:
- Gross monthly income: £5,500 (£66,000/year)
- Current monthly debt: £350 (car loan £220, credit card minimum £130)
- Proposed mortgage payment: £1,400/month
Current DTI (before mortgage):
350 / 5,500 × 100 = 6.4%
DTI with mortgage:
(350 + 1,400) / 5,500 × 100 = 1,750 / 5,500 × 100 = 31.8%
At 31.8%, you're in a strong position for approval.
How to Improve Your DTI
You can lower your DTI by either reducing debt or increasing income.
Reduce debt:
- Pay off the smallest debts first (frees up monthly payments quickly)
- Avoid taking on new debt before applying for a mortgage
- Pay more than minimums on credit cards
- Consider consolidating high-interest debt at a lower rate
Increase income:
- Take on freelance work or part-time income
- Ask for a pay rise or promotion
- Include bonus income if you can document it
Don't do this: Opening new credit accounts doesn't help your DTI — and each hard inquiry slightly reduces your credit score.
DTI vs Credit Score
These are related but different. A good credit score doesn't automatically mean a good DTI, and vice versa.
| Measures | Affects | |
|---|---|---|
| DTI | Debt burden relative to income | Loan approval, loan size |
| Credit score | Credit history, payment reliability | Interest rate offered |
A lender looks at both. High credit score + high DTI = declined. Low DTI + poor credit score = declined. You need both in good shape.
DTI When Self-Employed
Self-employed applicants typically need to provide 2–3 years of tax returns. Lenders use your net income (after business expenses), not your revenue — which can significantly affect your DTI calculation.
Tip: If you're planning to buy property and you're self-employed, work with an accountant to ensure your tax returns accurately reflect your income in the years leading up to your application.