Credit & Debt
How To Calculate Debt-To-Income Ratio
The debt-to-income ratio answers the question a lender is actually asking: not how much you owe, but whether the monthly payments fit inside your income. It takes two numbers and it decides mortgage approvals.
Quick Answer
DTI = Total Monthly Debt Payments / Gross Monthly Income
- DTI
- Debt-to-income ratio, usually expressed as a percentage
- Gross income
- Monthly income before taxes and deductions, not take-home pay
- Debt payments
- Contractual monthly obligations: housing, loans, support payments
- Front-end
- Housing expenses divided by income, often held to 28%
- Back-end
- All debts divided by income, often held to 36%
Debt-to-income divides your recurring monthly debt obligations by your gross monthly income before taxes, expressed as a percentage. Front-end counts housing costs only; back-end counts every debt. A borrower paying $2,620 a month on $7,200 gross has a 36.4% back-end ratio.
What Is Debt-To-Income Ratio?
Debt-to-income is a coverage ratio. It compares what must leave your account every month against what arrives, using gross income so that two borrowers in different tax situations are compared on equal footing. Nothing about total balances, credit score or savings enters the calculation — which is exactly why it is useful and also why it is incomplete.
Two variants exist and lenders read both. The front-end ratio counts housing only: mortgage principal and interest, property taxes, homeowners insurance, and association dues — the components lenders bundle as PITIA. The back-end ratio counts housing plus every other contractual obligation: auto loans, student loans, credit card minimums, child support and alimony. Convention caps these near 28% and 36% respectively, which is why the pair gets called the 28/36 rule.
Those thresholds came out of conforming mortgage underwriting rather than statute. The 'qualified mortgage' rule issued by the Consumer Financial Protection Bureau set a general back-end ceiling of 43%, with exceptions for loans that meet stricter agency criteria. Individual lenders layer their own overlays on top, so the effective ceiling depends on loan program and down payment rather than one universal number.
Note carefully what is excluded. Groceries, utilities, fuel, health insurance premiums, child care and subscriptions are not debts, because you can cancel them. Using take-home pay instead of gross income inflates the ratio substantially: someone earning $7,200 gross might deposit $5,300 after taxes, and dividing the same $2,620 of obligations by $5,300 turns a borderline 36.4% into a disqualifying 49.4%. Every underwriter uses gross income for this reason.
The practical consequence is that the ratio is one of the few numbers you can move deliberately. Debts are fixed obligations with known balances, so paying off a $12,400 auto loan removes its $340 payment and drops the back-end ratio by several points in a single month — leverage that no amount of income negotiation can match in the same timeframe.
What DTI cannot measure is whether the leftover income is enough to live on. A household at 35% still has 65% of gross income remaining, but whether that covers food, transport and child care depends entirely on local costs. The ratio screens for borrower risk; it does not budget for a household.
Formula
DTI = Total monthly debt payments / Gross monthly income
Add every contractual monthly obligation and divide by monthly income before tax. Multiply by 100 for the percentage lenders quote.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| D | Total monthly debt payments | currency | Housing plus auto loans, student loans, credit card minimums and court-ordered support. Excludes utilities, food and insurance. |
| I(gross) | Gross monthly income | currency | Income before taxes, taken from pay stubs for hourly or salaried work, or averaged over 24 months for self-employment. |
Front-end = Monthly housing expense / Gross monthly income
Housing alone. Conventional underwriting typically holds this near 28%.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| H | Monthly housing expense | currency | Principal, interest, property taxes, homeowners insurance and association dues. |
Headroom = (Target ratio x Gross income) - Current debt payments
How much additional monthly obligation fits before hitting a threshold — or how much must be cut if already over.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| t | Target back-end ratio as a decimal | decimal | 0.36 for the conventional guideline, 0.43 for the qualified mortgage ceiling. |
How To Calculate Debt-To-Income Ratio
- 1
Determine gross monthly income
Before taxes. Salaried borrowers divide annual pay by 12. Hourly workers multiply the hourly rate by average weekly hours, then by 52, then divide by 12 — use averaged overtime only if the lender permits it. Self-employed borrowers generally average two years of net profit.
- 2
Add up contractual debt payments only
Housing, auto loans, student loans, personal loans, credit card minimums, court-ordered support. Skip groceries, utilities, phone bills, fuel and insurance premiums — those are expenses you can cancel, not debts a lender counts.
- 3
Compute the front-end ratio
Divide housing cost by gross income. With $1,850 housing on $7,200 gross, that is 1,850 / 7,200 = 0.25694, or 25.7%. Conventional guidance keeps this near 28%.
- 4
Compute the back-end ratio
Divide total obligations by the same gross income. Here: $2,620 / $7,200 = 0.36389, or 36.4%. This is the number that usually decides the application.
- 5
Compare against headroom, not just the threshold
At a 36% guideline, this income supports $2,592 of obligations; the borrower carries $2,620, so they are $28 per month over. That is a solvable gap — paying off one loan or trimming a balance changes the answer immediately.
Examples
Example 1: Current obligations — housing plus three loans
- Gross monthly income
- $7,200
- Housing (PITIA)
- $1,850
- Auto loan
- $340
- Student loan
- $280
- Credit card minimum
- $150
| Step | Calculation | Result |
|---|---|---|
| Front-end ratio | $1,850 ÷ $7,200 | 0.25694 (25.69%) |
| Total monthly obligations | $1,850 + $340 + $280 + $150 | $2,620.00 |
| Back-end ratio | $2,620 ÷ $7,200 | 0.36389 (36.39%) |
| Headroom against the 36% guideline | (0.36 x $7,200) - $2,620 | -$28.00 |
Result: 25.69% front-end, 36.39% back-end — $28.00 over the 36% guideline
Example 2: After paying off the auto loan
- Gross monthly income
- $7,200
- Housing (PITIA)
- $1,850
- Student loan
- $280
- Credit card minimum
- $150
- Auto loan
- $0
| Step | Calculation | Result |
|---|---|---|
| New total obligations | $1,850 + $0 + $280 + $150 | $2,280.00 |
| Back-end ratio | $2,280 ÷ $7,200 | 0.31667 (31.67%) |
| Headroom against the 36% guideline | $2,592.00 - $2,280.00 | $312.00 |
Result: 31.67% back-end — $312.00 of headroom under the 36% guideline
Calculator
Back-end debt-to-income ratio
36.39%
- Front-end housing ratio
- 25.69%
- Total monthly obligations
- $2,620.00
- Headroom against the 36% guideline
- -$28.00
Values update as you type. This calculator covers the single scenario its formula assumes — see Common Mistakes for what it leaves out.
Prefer a full-width tool? Open the Debt-To-Income Ratio calculator page.
Common Mistakes
Dividing by take-home pay instead of gross income
Net income is smaller, so every ratio inflates. The same $2,620 of obligations reads 36.4% against gross but 49.4% against $5,300 take-home — a rejection that exists only as an arithmetic choice. Every lender uses gross.
Counting living expenses as debts
Utilities, groceries, fuel, phone plans and insurance premiums are not debts for this purpose. Including them can add hundreds of imaginary dollars to the numerator and push an otherwise clean application over the line.
Using statement balances instead of monthly payments
A $21,700 student loan balance is irrelevant here; only its $280 payment matters. Mixing the two overstates the ratio by orders of magnitude and is the most common self-assessment error.
Forgetting obligations absent from a credit report
Child support, alimony, co-signed loans and tax obligations count even when no bureau reports them. Lenders discover them during verification, and an undisclosed payment discovered late can collapse an approval.
Treating a passing front-end as a passing application
The borrower above clears the front-end 28% guideline easily at 25.7% and still fails the back-end at 36.4%. Both matter, and back-end is the one that carries more weight.
FAQ
What is considered a good debt-to-income ratio?
Below 36% is generally viewed favourably, with 36-43% workable depending on loan program, credit score and down payment. Above 43% typically fails conventional qualified-mortgage criteria, though some programs allow more.
Do I use gross or net income?
Gross — income before taxes and deductions. Lenders use gross so that borrowers in different tax brackets are compared consistently, and because payroll deductions do not represent money available to repay creditors.
Does the housing figure include taxes and insurance?
Yes. Count principal, interest, property taxes, homeowners insurance and any association dues as one housing figure. That is what lenders mean by PITIA, and omitting the escrow portion understates the front-end ratio badly.
How can I lower my DTI quickly?
Pay off small installment loans entirely, since removing the payment removes it from the numerator immediately. Increasing income helps more slowly, because lenders typically want two years of history for raises or new revenue.
Do student loans in deferment count?
Usually yes. Agency guidelines typically impute a payment — commonly around 1% of the balance, or a documented future payment — even though nothing is currently due. Ask how your loan program treats it before assuming zero.
References
- [1]Consumer Financial Protection Bureau, Ask CFPB, What is a debt-to-income ratio, and why does it matter? — https://www.consumerfinance.gov/ask-cfpb/what-is-a-debt-to-income-ratio-why-is-the-43-debt-to-income-ratio-important-en-1791/
- [2]Consumer Financial Protection Bureau, Ability-to-Repay and Qualified Mortgage Standards under Regulation Z — https://www.consumerfinance.gov/rules-policy/regulations/1026/43/
- [3]U.S. Department of Housing and Urban Development, FHA Single Family Housing Policy Handbook 4000.1 — https://www.hud.gov/program_offices/administration/hudclips/handbooks/hsgh