Debt-to-income ratio, usually shortened to DTI, compares your recurring monthly debt payments to your gross monthly income. It tells you how much of your income is already spoken for before groceries, gas, and everything else.
Use gross monthly income, not take-home pay
Most lenders calculate DTI using income before taxes and deductions. That is why the ratio can look healthier than your checking account feels. It is still a useful benchmark, but it is not the same thing as a comfort test.
Count recurring debts, not every living expense
Housing payment, minimum credit card payments, auto loans, student loans, personal loans, and other required monthly debts count. Utilities, groceries, and entertainment usually do not go into the standard DTI formula.
If gross monthly income is $6,500 and total recurring debt is $2,275, the back-end DTI is 35%. That means a little over one-third of gross income is already committed to debt payments.
Housing ratio vs back-end ratio
Some lenders look at the housing ratio by itself, which isolates the projected mortgage or rent payment. Others focus on the back-end ratio, which includes housing plus other debts. The back-end number usually matters more because it reflects the real monthly load.
Why 36% and 43% come up so often
Many underwriting conversations treat 36% as a comfortable zone and 43% as a line where approvals or terms can tighten. That does not mean everyone above 43% is denied, but it does mean the margin for error gets thinner.
DTI is not a full affordability answer
You can have a technically acceptable DTI and still feel stretched if childcare, transportation, medical costs, or irregular income are part of the picture. Use DTI as a screening tool, not the final word.
Use the calculator next
Add your projected housing payment and your recurring debt payments to see where your ratio lands. Then compare that number with your take-home pay and emergency fund plan before taking on something new.