Your credit score gets all the attention, but mortgage underwriters often pay closer attention to your debt-to-income ratio (DTI). It's the most direct measure of whether you can actually afford the loan you're applying for — and it's entirely within your control to improve.
DTI = Total Monthly Debt Payments ÷ Gross Monthly Income
Gross income means before taxes. Monthly debts include: minimum credit card payments (not your full balance), car loans, student loans, personal loans, and the proposed new mortgage payment. It does not include utilities, groceries, insurance, or other living expenses.
Front-end DTI (housing ratio): Only your proposed housing costs ÷ gross income. This includes PITI — principal, interest, property taxes, and homeowner's insurance. Most lenders want this below 28%.
Back-end DTI (total debt ratio): All monthly debt payments including housing ÷ gross income. This is the primary qualifying ratio. The maximum for most conventional loans is 43%, though some lenders go to 45–50% with strong compensating factors (high credit score, large down payment, substantial cash reserves).
Below 36%: Excellent. Most lenders view this as low-risk and you'll likely qualify for the best rates available.
36–43%: Acceptable. You'll qualify for most conventional loans but may not access the absolute best rates.
43–50%: High. Conventional lenders may decline. FHA or VA loans may still be available. Expect higher rates.
Above 50%: Very difficult. You'll need to reduce debt before most lenders will consider your application.
You can lower DTI from either direction: reduce debt payments or increase income.
Eliminate a car payment: Paying off a $400/month car loan has the same DTI effect as earning $1,000 more per month (in a 40% tax bracket). Car payments are the single most efficient debt to eliminate before applying for a mortgage.
Pay down credit cards: The minimum payment on a $5,000 balance might only be $100–125/month — but once it's paid off, that $100 disappears from your DTI calculation.
Avoid new debt: In the 12 months before a mortgage application, don't take on new car loans, personal loans, or significant new credit card balances. Each new monthly obligation adds directly to your back-end DTI.
Increase income: A side job, freelance work, or raise that increases gross monthly income lowers DTI from the other direction. Document any new income for at least 2 years to have lenders count it (with some exceptions for certain income types).
Calculate your current DTI with the Debt-to-Income Calculator.
Ready to run your own numbers? Use the free DTI Calculator — no signup required.