Debt-to-Income Ratio: The Number That Decides Your Mortgage Approval

Maya earns $6,500 a month before tax and wants a $350,000 house. She has $35,000 saved, a clean payment history, and a lender who says her application is “close but over the limit.” The limit is her debt-to-income ratio. Her ratio comes out at 52.6%, and the lender’s cap in this example is 43%.

Debt-to-income (DTI) is your monthly debt payments divided by your gross monthly income. Lenders run it twice: once on the new housing payment alone, once on every debt including that payment. The second figure usually decides the answer.

Key points

• DTI is monthly debt payments divided by gross (pre-tax) monthly income. Maya’s $3,416 of total payments on $6,500 of income gives 52.6%.
• The “front-end” ratio counts only housing costs (39.9% for Maya). The “back-end” ratio adds car, student and card payments (52.6%).
• At an illustrative 43% cap, Maya’s $820 a month of existing debt limits her to roughly a $224,000 loan, not the $315,000 she wanted.
• Paying off a card with a $90 minimum raises her limit by about $13,000 in this example, because lenders count the payment, not the balance.
• The cap itself is a lender or loan-program choice. This article uses 43% as an assumption, not as a rule you can count on.

What exactly goes into the DTI formula?

Numerator: recurring monthly debt payments. Denominator: gross monthly income. That’s all of it.

Maya’s side of the ledger, before any mortgage:

Her existing-debt ratio is $820 ÷ $6,500 = 12.6%. Nothing alarming. The trouble starts when the mortgage joins the list.

Two details trip people up. First, income is gross, so Maya’s take-home pay doesn’t matter here. Second, the card counts at its minimum payment, not its balance. A $2,800 balance and a $2,800,000 balance would both be entered as whatever the statement says you owe each month.

Groceries, utilities, phone, insurance premiums outside the mortgage, and subscriptions don’t appear. They are real costs, but they aren’t debts, so the ratio ignores them. Keep that in mind; we come back to it near the end.

How big is the new mortgage payment, really?

Bigger than the loan payment alone. Lenders count the whole housing bill, usually abbreviated PITI: principal, interest, taxes, insurance. Add mortgage insurance if the down payment is under 20%.

Here are Maya’s assumptions. They’re illustrations, not quotes:

• Price $350,000, down payment 10% ($35,000), loan $315,000
• 30-year fixed at a 6.5% interest rate
• Property tax $3,850 a year, home insurance $1,500 a year
• Mortgage insurance at 0.6% of the loan a year

The arithmetic:

• Principal and interest: the standard amortization formula at 6.5% over 360 months gives $6.3207 per $1,000 borrowed. On $315,000 that’s $1,991 a month.
• Property tax: $3,850 ÷ 12 = $322
• Insurance: $1,500 ÷ 12 = $125
• Mortgage insurance: 0.6% × $315,000 = $1,890 a year, or $158 a month
• Housing total: $1,991 + $322 + $125 + $158 = $2,596

Front-end DTI: $2,596 ÷ $6,500 = 39.9%.

Back-end DTI: ($2,596 + $820) ÷ $6,500 = $3,416 ÷ $6,500 = 52.6%.

Some lenders will stop at the front-end figure and be happy. Many will look at the back-end figure and stop there. Maya’s lender looked at the back-end one.

Which interest rate does the lender use: the rate or the APR?

The payment comes from the note rate, not the APR. That matters for your own math.

The Consumer Financial Protection Bureau explains that the APR reflects the interest rate, any points, mortgage broker fees, and other charges, which is why the APR is usually higher than the interest rate alone. The interest rate, by contrast, is the yearly cost of borrowing the money and “does not reflect fees or any other charges.”

The monthly payment you owe is built from the interest rate on the loan. So when you reverse-engineer your own DTI, use the rate from page 1 of the Loan Estimate, not the APR from page 3. Using the APR overstates your payment slightly. That isn’t harmful for a rough check, but it won’t match the lender’s number.

One caution from the same CFPB page: for adjustable-rate loans, the APR doesn’t reflect the maximum interest rate the loan could reach. A DTI that works at today’s starting rate can stop working after a reset. Lenders deal with this in different ways, and this article can’t tell you which way yours will.

What loan size does a 43% cap actually allow?

Reverse the formula. If the cap is 43% of $6,500, total monthly debt can’t exceed $2,795. Subtract Maya’s $820 of existing payments and $1,975 is left for housing.

Her fixed housing costs are tax and insurance, $447. That leaves $1,528 for principal, interest and mortgage insurance combined. Each dollar of loan costs $0.0063207 a month in principal and interest plus $0.0005 in mortgage insurance, so $0.0068207 in total:

$1,528 ÷ 0.0068207 = about $224,000

Check it. A $224,000 loan costs $1,416 in principal and interest, $112 in mortgage insurance, plus $447 for tax and insurance. That’s $1,975 for housing, and ($1,975 + $820) ÷ $6,500 = 43.0%.

Maya’s $315,000 target is $91,000 above that. Her income, her savings and her credit history didn’t change. Only the debt payments did the damage.

(A simplification: this holds property tax at $322 a month even as the house gets cheaper. In reality a cheaper house usually carries a lower tax bill, so the true limit would sit slightly above $224,000. The direction of the result doesn’t change.)

Which fix moves the number most?

Four changes Maya could test, each run through the same formula with everything else held fixed:

Each row’s loan limit comes from the same steps as above. Take the card payoff: $2,795 − $730 = $2,065 of housing room; minus $447 is $1,618; divided by 0.0068207 is about $237,200. The raise works the same way with a $3,010 total allowance ($7,000 × 0.43).

Three things stand out.

The card is cheap leverage. Maya’s card has a $2,800 balance and a $90 minimum. Clearing it costs $2,800 in cash and lifts her limit by $13,200. That’s close to $4.70 of extra borrowing power per dollar paid. The mortgage payment counts, and her card payment of $90 is replaced by nothing.

It also costs her in other ways. The Consumer Financial Protection Bureau notes that card issuers generally compute interest by dividing the APR by 360 or 365 and applying it to the end-of-day balance, so the interest compounds daily. At an assumed 24% APR the daily rate is about 0.066%, and a $2,800 balance is accruing roughly $56 a month. Paying it off helps her DTI and stops that bleed at the same time. Rare moment where both goals agree.

The car loan moves the most. Clearing $420 a month adds about $61,600 to her loan limit. It also needs the biggest cash outlay: assume a $9,000 payoff balance, and she’d spend a quarter of her $35,000 savings. Lenders look at what’s left after closing, not only at the ratio, so the cash she spends to improve one number may weaken another.

Why does the lender care about this number at all?

Because the ratio is a rough measure of how much of each paycheck is already spoken for. A person who sends 52.6% of gross income to creditors has less room when the water heater breaks or hours get cut. Lenders have seen that pattern end in missed payments.

That’s the logic. I can’t give you a loss rate for each DTI band, because the sources I used don’t contain one and I’d rather leave it out than invent it. The point of the cap is risk control, and each lender or loan program sets its own line.

What this does not tell you

Treat the numbers above as a model, not a prediction.

• The 43% cap is an assumption. Some programs allow higher ratios with strong credit or reserves. Some lenders set lower ones. Your own approval depends on the lender’s rules, which I haven’t seen.
• Gross income hides taxes. Maya’s $6,500 is before tax. A buyer in a high-tax state with a $2,596 housing bill may feel far more squeezed than one with the same ratio in a low-tax state.
• Non-debt costs are invisible. Childcare, health premiums, commuting and food don’t enter DTI. A ratio of 40% can feel fine for one household and impossible for another.
• Income must be provable. Lenders generally count income they can document. Bonus, freelance or part-time earnings may count less or not at all, depending on history.
• Other credit items matter. Credit score, down payment size, cash reserves and employment history all sit beside DTI. Passing the ratio doesn’t mean approval.
• Figures are illustrations. The rate, tax, insurance and mortgage insurance numbers are assumptions chosen to be realistic, not quotes. Rerun the arithmetic with the numbers on your own Loan Estimate.

FAQ

What is a good debt-to-income ratio for a mortgage?

There’s no single number. Lower is safer for the lender and for you. This article used 43% as an illustrative cap, but actual limits vary by loan program and lender, and some will approve higher ratios when other factors are strong. Ask any lender you talk to what their back-end limit is for the loan type you want.

Do utilities, groceries and insurance count as debt?

No. DTI only counts recurring debt obligations such as loans, card minimums and the proposed mortgage payment. Utilities, food and subscriptions are left out, which is why the ratio can look comfortable while your monthly budget is tight.

Does the credit card balance or the minimum payment count?

The minimum payment is what usually gets entered. That is why paying a card down to zero helps your ratio, while paying it down by half might not help at all if the minimum barely changes. Check how your card’s minimum is calculated, and ask the lender what figure they’ll use.

Should I use the interest rate or the APR to estimate my payment?

Use the interest rate. The Consumer Financial Protection Bureau says the APR includes points, broker fees and other charges and is a broader measure of borrowing cost. The payment itself is calculated from the interest rate. The APR is better for comparing loan offers than for computing a monthly payment.

Does a bigger down payment fix a high DTI?

It helps, but less than people expect. A larger down payment shrinks the loan, so principal and interest drop, and it can remove or reduce mortgage insurance. In Maya’s case, 20% down ($70,000) would cut the loan to $280,000 and eliminate the mortgage insurance line. But her existing $820 of debt still takes the same bite out of her income, and the savings she spends may reduce her reserves.

Does my spouse’s income and debt count?

If you apply together, generally yes: both incomes and both sets of debts go into the ratio. A partner with high income and no debts can lower the blended figure. A partner with high debts can raise it. Rules vary by lender and by who is on the loan, so confirm before you assume.

What should you look at next?

Pull your last three statements and total every payment that shows up each month. Divide by your gross monthly income. That’s your existing-debt ratio, and it’s the one piece you can compute today without a lender.

Then take the Loan Estimate from any lender who has run your numbers and find two figures: the interest rate on page 1 and the APR on page 3. Rebuild the monthly payment yourself from the rate and the loan amount, then add tax, insurance and any mortgage insurance. If your total matches theirs within a few dollars, you understand what they’re measuring.

Last, rerun the arithmetic with one debt removed and one with your income changed by a realistic amount. Which line moves the answer most for you? That tells you where the leverage is, whichever direction you choose to take.

This article is general information, not financial advice. See our disclaimer.

Read next

• How One Extra Mortgage Payment Per Year Cuts Total Interest
• Mortgage Points Breakeven: How Long Until Buying Down Your Rate Pays Off
• Car Loan vs Cash: The Total Interest You Pay to Drive
• The Minimum Payment Trap: How Long It Actually Takes to Clear

Also worth reading: Amortization Schedules: Why Your Early Payments Are Almost All Interest

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