What Is Debt-to-Income Ratio (DTI)?

When you apply for a mortgage, a car loan, or sometimes even a credit card, the lender will look at your debt-to-income ratio, often shortened to DTI. It’s one of those numbers that can feel a bit abstract until you see how it’s used: lenders use it to decide whether you can afford to take on more debt, and if so, how much.

In plain terms, DTI is the share of your gross (before-tax) monthly income that goes toward debt payments. If you make $5,000 a month and pay $1,500 toward debt, your DTI is 30%. The higher that percentage, the less “room” the lender thinks you have for another payment. So understanding DTI helps you see your situation the way a bank does, and it can help you plan before you apply.

To get your DTI, you add up all the monthly debt payments you’re required to make. That usually includes things like your current rent or mortgage, car loans, student loans, minimum payments on credit cards, and any other loans with a monthly obligation. You don’t include utilities, groceries, or other spending that isn’t a contractual debt payment.

You take that total and divide it by your gross monthly income (your pay before taxes and other deductions). If you’re salaried, you can use your annual salary divided by 12. If you have bonuses or side income that you use for debt, some lenders will count that too, but they often average it or use conservative rules. Multiply the result by 100 and you get your DTI as a percentage.

For example, say your gross income is $6,000 per month. Your rent is $1,400, your car payment is $350, and your student loan is $200. That’s $1,950 in debt payments. $1,950 ÷ $6,000 = 0.325, or 32.5% DTI. That’s the number a lender would use when judging whether you can handle a new mortgage payment on top of what you already pay.

You’ll sometimes hear “front-end” and “back-end” DTI. They’re the same idea (debt payments as a share of income) but they use different definitions of “debt.”

Front-end DTI uses only your housing payment. So it’s housing divided by gross monthly income. It answers: how much of your paycheck goes to keeping a roof over your head? Conventional wisdom often cites 28% as a guideline: try to keep housing at or below 28% of gross income. That’s not a law; some programs allow higher. But it’s a common benchmark.

Back-end DTI uses housing plus all your other monthly debt. So it’s the full picture: housing, car, student loans, credit cards, etc., all divided by gross income. Lenders care about this because it shows how much of your income is already spoken for. Many like to see back-end DTI at or below 36%, though again, limits vary. When you apply for a mortgage, the lender will check both. Your new housing payment can’t push you over their front-end limit, and your total debt (including that new payment) can’t push you over their back-end limit.

For a mortgage in particular, the lender is asking: if we give you this loan, will your total debt load stay within our limits? So they’ll look at your current debt, add in the new housing payment (principal, interest, taxes, insurance, HOA), and see where your back-end DTI lands. If it’s too high, they may offer a smaller loan, ask for a larger down payment, or decline.

A lower DTI often helps. It can improve your chances of approval and sometimes your interest rate, because the lender sees less risk that you’ll be overstretched. So if you’re planning to buy in the next year or two, it can be worth paying down other debt or avoiding new debt so that when you apply, your DTI leaves room for the house payment you want.

You don’t have to guess the number. You can add up your payments and your income and run the math yourself, or use a Mortgage Affordability Calculator to see how different incomes and debt levels affect what you can borrow. Once you know your DTI and your lender’s general limits, you have a clearer picture of how much house you can afford and what might need to change to get there.