Debt Ratio Calculator: What Your DTI Says About Your Borrowing Power
Lenders don't just ask what you earn. They ask what you already owe each month before they hand you one more payment. That comparison, monthly debts divided by monthly income, is your debt-to-income ratio, or DTI. This debt-to-income ratio calculator works it out from your own income and debts. It helps decide whether a mortgage gets approved and how much house you can buy.
What DTI is, and why lenders care so much
DTI is a share of your income. Add up everything you must pay each month toward debts, divide by gross monthly income, and multiply by 100. A DTI of 35% means 35 cents of every dollar you earn is already promised elsewhere. Lenders rely on this number because it survives salary inflation: a person earning $40,000 with no debts can be a safer bet than one earning $150,000 with five big payments. Income tells a lender what you could pay; DTI tells them what you can still pay. It is also a stress test. Cars break and hours get cut, and the ratio shows whether the payments still fit afterward.
Front-end vs back-end: the two ratios that matter
Most borrowers meet two versions of DTI, and mixing them up is the easiest way to misread your finances. The front-end ratio counts housing only: rent, or a mortgage payment plus property tax and insurance, divided by gross monthly income. It answers one question: how much of your pay does your roof eat? The back-end ratio counts everything: housing plus every other monthly debt. It answers the bigger question: how much of your pay is already gone?
Lenders check both because each catches something the other misses. A cheap apartment with crushing student loans looks fine on the front end and terrible on the back end. The classic guideline, often written as 28/36, caps the front end at 28% and the back end at 36%, the lines most underwriters start from.
Every input, explained
Gross income, before tax. Your pay before taxes and deductions, the figure on your pay stub. Don't enter take-home pay; that inflates your DTI. Still, run a second, private check on net pay later: a ratio that looks fine on gross can feel tight on what actually lands in your account.
Housing cost, fully loaded. Rent, if you rent. If you own or are buying, the full monthly payment: mortgage principal and interest, property taxes, and homeowner's insurance. Leaving out tax and insurance flatters your ratio by hundreds of dollars a month.
Car, student loans, other debts. Enter each required monthly payment exactly as billed, not the total balance. A $40,000 student loan sounds scary, but it's the $200 monthly payment that moves your DTI. If the car is paid off, it's zero. "Other" covers anything else with a required payment: personal loans, child support, a financed phone plan. Groceries and utilities don't count.
Credit-card minimums, not balances. This is the field people get wrong most often. DTI uses the minimum payment your card issuer requires each month, not the balance you carry or the amount you usually pay. A $5,000 balance with a $120 minimum counts as $120.
A worked example: $84,000 a year, $1,800 of housing
- Gross monthly income: $84,000 ÷ 12 = $7,000.
- Housing: $1,800 a month, including tax and insurance.
- Other monthly debts: car $350 + student loans $200 + credit-card minimums $120 + other $0 = $670.
- Total monthly debts: $1,800 + $670 = $2,470.
- Front-end DTI: $1,800 ÷ $7,000 = 25.7%, inside the classic 28% guideline.
- Back-end DTI: $2,470 ÷ $7,000 = 35.3%, just inside the classic 36% cap.
- Headroom at 36%: the cap allows 36% × $7,000 = $2,520 of total debts, so this household has only $50 a month of headroom. One new payment breaks it.
- Headroom at 43%: some lenders allow up to 43%, permitting 43% × $7,000 = $3,010 of monthly debts, which is $540 a month of headroom. Room on paper, with little slack.
- Reverse check: what income carries $1,800 of housing at the 28% rule? $1,800 × 12 ÷ 0.28 = about $77,143 a year. At $84,000, this household clears that bar. Housing isn't the problem. The other debts are.
Why headroom matters: look at that $50 again. It means this household, healthy-looking at 35.3%, cannot take on a single new payment, not a $200 car payment and not a $150 furniture plan, without crossing the 36% line.
What happens if housing rises?
Housing is the biggest lever on your DTI, and the one most likely to move, through a rent renewal or a bigger place. This table holds everything else fixed (the same $670 of other debts, the same $7,000 income) and changes only housing.
| Monthly housing | Total monthly debts | Back-end DTI | Verdict |
|---|---|---|---|
| $1,500 | $2,170 | 31.0% | Comfortable, with solid headroom |
| $1,800 | $2,470 | 35.3% | Inside 36%, but only $50 of headroom |
| $2,100 | $2,770 | 39.6% | Over the 36% guideline |
| $2,400 | $3,070 | 43.9% | Over even the looser 43% ceiling |
A $300 housing increase, the kind of jump one rent renewal can deliver, moves this household from just inside the guideline to clearly over it. If your housing is about to rise, run the calculator on the new figure before you sign, not after.
Lender comfort bands: where do you sit?
No single DTI number is a pass or fail on its own, because lenders weigh credit score, savings, and down payment too. But these bands map how most underwriters react.
| Back-end DTI | How lenders usually see it |
|---|---|
| Under 28% | Strong. Plenty of slack. |
| 28% to 36% | Comfortable. Inside the classic guideline. |
| 36% to 43% | Tight but possible, with good credit or solid reserves. |
| 43% to 50% | Stretched. Approval gets hard without a compensating factor. |
| Over 50% | Very hard to borrow until debts fall or income rises. |
Notice the gap between "a lender will approve you" and "you can comfortably afford this." At 43%, nearly half your gross pay is committed before you eat. Treat 36% as your personal ceiling even when a lender offers more.
Common mistakes that skew your DTI
- Using net pay instead of gross. It feels more honest, but lenders use gross. Use gross officially, then run a private net-pay version for yourself.
- Forgetting credit-card minimums. People enter balances, or what they usually pay, or nothing at all. DTI wants the required minimum. Even a small $120 minimum matters: here it's part of the $670 that leaves only $50 of headroom.
- Counting a mortgage without tax and insurance. A $1,400 loan payment with $250 of tax and $150 of insurance is a $1,800 housing cost, not $1,400. Enter the smaller figure and your front-end ratio understates reality by more than four points on a $7,000 income.
- Treating 43% as comfortable. It's a ceiling some lenders allow, not a target. A household approved at 43% has almost no room for a surprise.
- Leaving out "small" debts. A $60 personal loan, a $40 store card, a $90 payment plan: each looks trivial alone. Together they eat your headroom. If it's a required monthly payment, it counts.
Practical tips: moving your ratio in the right direction
If your DTI is higher than you'd like, don't start with the biggest debt: start with the one you can kill. In our example, the $670 of non-housing debt is the lever. Paying off the card minimums first (that $120) drops the back-end ratio from 35.3% to 33.6% and more than triples headroom at the 36% cap, from $50 to $170.
Think twice before adding any payment when headroom is thin. With only $50 of room at the 36% cap, financing a car at $250 a month blows straight past the guideline to about 38.9%. If you need the car, pay something down first, or wait until a debt is gone. And re-run the calculator after any raise: a $6,000 annual raise adds $500 to monthly gross income and drops this household's ratio from 35.3% to about 33.0% without paying off a single debt.
Frequently asked questions
What's a good DTI ratio?
For most borrowers, a back-end DTI under 36% is the comfortable zone, with a front-end ratio under 28%. Some lenders approve up to 43% or even 50% with strengths like a high credit score, but approval isn't the same as comfort.
Should I use gross or net income for DTI?
Use gross income, your pay before taxes and deductions, because that's what lenders use. Using net pay makes your ratio look higher than a lender's version. Still, compute a private version on take-home pay too.
Do credit-card balances count, or just minimum payments?
Only the required minimum monthly payment counts toward DTI, not the full balance. A $5,000 balance with a $120 minimum counts as $120.
Can I get a mortgage with a DTI over 43%?
Sometimes, but it's an uphill climb. Some programs allow up to 45% or 50% with strong compensating factors: excellent credit or substantial reserves. If you're over that line, paying down a small debt or two before applying often helps.
Does DTI include rent, or only mortgages?
Both. The front-end ratio uses whatever your housing cost is: rent, or the full mortgage payment including taxes and insurance. When applying for a mortgage, lenders use the proposed new payment, not your current rent.
Related calculators: House Affordability Calculator, Mortgage Calculator and Credit Card Payoff Calculator.
A ratio is a snapshot, not a plan. Payoff timelines and card debt get the longer treatment on the CalcMega Blog.
General information only: lending criteria vary by lender and loan program. Nothing here is financial advice.
Lenders explain debt-to-income limits the same way in the Consumer Financial Protection Bureau's home-buying guide.