💳 How to Calculate Debt-to-Income Ratio (DTI)

When you apply for a loan, the lender is really asking one question: after your existing debts, is there enough of your income left to cover a new payment? The debt-to-income ratio, or DTI, turns that question into a single percentage. It compares what you owe each month with what you earn each month, and it plays a major role in whether a mortgage, car loan or personal loan gets approved — and sometimes in the interest rate you are offered.

The DTI formula

The formula is simple:

DTI = (total monthly debt payments ÷ gross monthly income) × 100

Two details matter. First, use your gross income — what you earn before tax, not your take-home pay. If you are salaried, divide your annual gross salary by 12. If your income varies, use an average of recent months. Second, count every recurring monthly debt payment: rent or mortgage, car loan, student loan, personal loan, and the minimum payments on your credit cards. Everyday spending — groceries, subscriptions, utilities — does not count, because it is not debt.

Front-end vs back-end DTI

Lenders actually use two versions. Front-end DTI counts housing costs only: rent or mortgage payment plus property taxes, homeowner's insurance and any homeowner association dues, divided by gross monthly income. Back-end DTI counts all monthly debt payments, housing included, divided by the same income. When people say "my DTI is 40%", they usually mean the back-end figure, and it is the one lenders weigh most heavily.

Worked example

Take someone earning $5,000 gross per month. Their monthly debts are: rent $1,400, a car loan payment of $300, a credit card minimum of $150, and a student loan payment of $200. Total monthly debt = $2,050.

Back-end DTI = ($2,050 ÷ $5,000) × 100 = 41%. Front-end DTI = ($1,400 ÷ $5,000) × 100 = 28%. So housing alone takes 28% of gross income, and all debts together take 41%.

What is a good DTI?

Lower is always better, because it means more of your income is free. As a general guideline, many lenders look for a back-end DTI of 36% or less, and a front-end DTI of 28% or less — the classic "28/36 rule" used in mortgage lending. That said, it is a guideline, not a law: some loan programs accept higher ratios when other factors are strong, such as a large down payment, a high credit score, or substantial savings. Check current lender requirements before applying, since programs and thresholds change. A back-end ratio above 50% is a warning sign in any case — it leaves very little room for emergencies, and most lenders will see it the same way.

What counts — and what does not

One trap catches many borrowers: credit cards. Lenders use the minimum payment on your statement, not your balance and not the amount you actually pay. So a card with a $4,000 balance and a $100 minimum counts as $100, even if you pay the full $4,000 each month. Child support and alimony payments also count as debts. On the other hand, money you choose to save, invest or spend on living costs does not count — only fixed, recurring debt obligations do.

How to lower your DTI

You can move the ratio from either side. Paying off a debt removes its whole monthly payment from the numerator, which is why clearing one small loan entirely often helps more than slightly reducing several large ones. On the income side, a raise, a second job or documented side income grows the denominator. And if you are planning to borrow, avoid taking on new debt — a fresh car loan or a new card — in the months before you apply, since every new payment pushes your ratio up. If you want a payoff plan, try our free Debt Payoff Calculator to see how extra payments change your timeline.