How DTI is calculated
The Consumer Financial Protection Bureau defines DTI exactly this way: all your monthly debt payments divided by your gross monthly income. Lenders look at two versions. The front-end ratio uses only the housing payment. The back-end ratio, also called total DTI, adds every other required monthly payment. When people say "DTI" without a qualifier they almost always mean the back-end ratio.
Checking your debts outside a home purchase, with your current rent and bills? Bill Organizer's debt-to-income ratio calculator covers everyday budgeting; this page is built around what a mortgage lender counts.
How this calculator works, in plain language
Lenders want to know how much of each month's pay is already spoken for. The calculator adds up every monthly payment you owe, divides it by what you earn before tax, and shows the result as a percentage. It does that twice: once with only the housing payment (front-end), and once with every debt (back-end). Then it works backwards from the limit you pick: whatever that percentage of your income leaves after your other debts is the largest housing payment that still fits. It doesn't look at your credit score, savings or the loan type, which lenders weigh too.
Worked example
Using the CFPB's own numbers: a $1,500 mortgage payment, a $100 car payment and $400 of other debt payments add up to $2,000 a month. On a gross income of $6,000 a month ($72,000 a year), the back-end DTI is 33.3% and the front-end DTI is 25%. To stay at 36% with the same $500 of other debts, the housing payment could be up to $1,660.
DTI by scenario
Six households, run through the same formula as the calculator. The band column compares the back-end ratio with Fannie Mae's maximums in Selling Guide B3-6-02 (section dated April 2, 2025, checked October 2, 2026); the last column is the largest housing payment that keeps the back-end ratio at 36% with the same other debts.
| Household | Gross income /mo | Housing | Other debts | Front-end | Back-end | Fannie Mae band | Max housing at 36% |
|---|---|---|---|---|---|---|---|
| CFPB example: $72,000 salary | $6,000 | $1,500 | $500 | 25% | 33.3% | Within 36% (manual) | $1,660 |
| Renter planning a first home | $7,500 | $2,100 | $200 | 28% | 30.7% | Within 36% (manual) | $2,500 |
| Two incomes, car and card payments | $11,000 | $2,800 | $600 | 25.5% | 30.9% | Within 36% (manual) | $3,360 |
| First-time buyer with student and car loans | $4,500 | $1,350 | $550 | 30% | 42.2% | 36–45% (manual with credit and reserves) | $1,070 |
| Larger payment on a moderate income | $6,000 | $2,300 | $500 | 38.3% | 46.7% | 45–50% (DU only) | $1,660 |
| High debts relative to income | $5,000 | $1,600 | $1,000 | 32% | 52% | Over 50% | $800 |
DTI limits lenders use (2026)
Fannie Mae's Selling Guide B3-6-02, Debt-to-Income Ratios (current guide published September 2026) sets these maximums for conventional loans it buys:
- 36% of stable monthly income for manually underwritten loans.
- Up to 45% for manually underwritten loans when the borrower meets the credit score and reserve requirements in Fannie Mae's Eligibility Matrix.
- 50% for loan casefiles approved through Desktop Underwriter (DU), Fannie Mae's automated system.
FHA, VA and USDA loans follow their own agency rules, and individual lenders can be stricter than the agency. The 28% front-end figure in the familiar 28/36 rule is a planning guideline rather than a Fannie Mae limit. Use the limit selector above to see the payment each ratio allows.
Common DTI mistakes
- Using take-home pay. DTI divides by gross income. Using net pay makes the ratio look worse than the lender will calculate it, and it hides how tight the budget really is.
- Leaving taxes, insurance and mortgage insurance out of the housing payment. Lenders count the full monthly housing cost, not just principal and interest. On a typical loan that can add several hundred dollars a month.
- Counting balances instead of payments. DTI uses the required monthly payment on each debt, such as a card's minimum, not the amount you owe.
- Adding everyday bills. Utilities, phone, groceries and car insurance aren't debts in DTI, even though they come out of the same paycheck.
- Forgetting support and co-signed obligations. Alimony and child support you pay count when they continue beyond ten months, as do other recurring obligations listed in Fannie Mae's guide.
- Treating the maximum as a target. A ratio a lender will approve can still leave little room for saving, childcare or repairs. The 28/36 rule is a more cautious planning check.
How to lower your DTI
- Pay off small balances first. Removing a whole monthly payment, such as a nearly paid car loan, moves DTI more than paying down a large balance a little.
- Avoid new credit before you apply. A new car or card payment adds straight to the back-end ratio.
- Lower the housing payment. A larger down payment, a cheaper home or no PMI all reduce the front-end and back-end ratios together. Test prices in the mortgage calculator.
- Count all qualifying income. A co-borrower's income, or documented overtime and bonus history, can raise the denominator.
DTI ignores taxes, childcare, retirement saving, utilities and repairs, so a payment a lender approves is not automatically comfortable. This calculator is an estimate for planning, not a loan decision; your lender's figures are final.
