Debt-to-Income Ratio (DTI)

Your debt-to-income ratio — DTI for short — is the single most important approval metric after your credit score. It is not complicated: it is the share of your gross income that goes to debt each month. And unlike your credit score, which takes years to build, you can change your DTI in a matter of months. Here is how to calculate it, what number lenders want, and how to move it in your favor.

How to calculate your DTI

The formula is simple:

1. Add up all your monthly debt payments. That includes the mortgage payment you are applying for (the full PITI), plus car loans, student loans, personal loans, and the minimum payments on your credit cards.
2. Divide that total by your gross monthly income — your income before taxes and deductions.
3. Multiply by 100 to get a percentage.

Example: you earn $6,000 a month gross. Your future mortgage PITI is $1,800, your car payment is $400, and your student loan is $300. Total monthly debt is $2,500. $2,500 ÷ $6,000 = 0.417, or a 41.7% DTI.

Notice what is not counted: utilities, groceries, insurance other than homeowners, and any credit-card balance you pay in full each month. Only debt obligations you must pay every month count.

The numbers lenders want

Lenders actually look at DTI in two slices:

• Front-end ratio (housing only): your mortgage payment divided by gross income. Most lenders want this at 28% or less.
• Back-end ratio (all debt): everything, housing included. The standard conventional limit is 36%, though FHA allows up to 43% and some programs stretch to 50% for exceptionally strong borrowers.

The front-end is the familiar 28% rule. The back-end is the stricter gate — it is why a car payment or student loan directly shrinks how much house you can buy. On a $6,000 monthly income, a 36% back-end cap means $2,160 a month for all debt combined. If your car and student loans already eat $700, only $1,460 is left for housing.

Why your DTI matters so much

DTI is a predictor of default. Borrowers who spend a large share of income on debt have far less cushion for a job loss, a medical bill, or a rate reset — and they default more often. Lenders know this, so DTI does three things at once:

• Approval: cross the program's limit and you are declined, no matter how high your score.
• Pricing: a lower DTI can earn a slightly better rate and lower PMI.
• Your own safety: the same math that predicts default is also the math that predicts whether you will feel house-poor.

The last point is the one to internalize. The lender's DTI limit is about their risk. Your comfort level should be more conservative — most people sleep better well below the 36% ceiling.

How to improve your DTI before you apply

Because DTI is a ratio, you can improve it from either side — reduce debt or increase income — or both. The fastest, most controllable lever is debt:

• Pay down credit cards first. They are the most expensive debt and their minimum payments directly inflate your DTI. Paying off a card that required a $150 minimum drops your DTI by exactly that $150.
• Kill a car loan before buying. A $400 car payment is a huge monthly obligation. Paying it off just before you apply frees up that entire amount for housing.
• Consolidate or refinance debt to a lower monthly payment where it makes sense.

On the income side, any verifiable income counts: a raise, a second job, a co-borrower. But lenders want to see stable, documented income, so a one-off gig usually does not help. The debt side is where you have the most control in the shortest time.

A realistic example of the payoff

Take a couple earning $100,000 a year ($8,333 a month gross). They carry a $450 car payment and $350 in credit-card minimums.

• Before: $800 in other debt leaves room for about $2,200 of housing under a 36% back-end cap.
• After paying off the car and cards: the full $2,333 from the 28% rule becomes available, and their housing budget rises by over $130 a month — enough for roughly $20,000 more home.

Clearing a car loan and credit-card debt before applying does not just lower your DTI — it raises the exact number of dollars you can put toward the home itself.

Frequently asked questions

What is a good DTI for a mortgage?

Aim for a back-end DTI of 36% or less, with housing at 28% or less. Lower is always better for both approval and your budget.

Does DTI use gross or net income?

Gross — income before taxes and deductions. That is the number lenders use because it is consistent and verifiable.

What debts count toward DTI?

Recurring monthly obligations: mortgage or rent, car loans, student loans, personal loans, and credit-card minimums. Utilities, insurance, and balances paid in full each month do not.

Can I get approved with a high DTI?

Possibly, through FHA (up to 43%) or with strong compensating factors, but a high DTI usually means a worse rate and a payment that strains your budget. It is better to improve the ratio first.

Model your target payment against your income with the HomeMath mortgage calculator — it shows the income required under the 28% rule on every result.