Debt-to-Income Ratio Calculator - Front & Back-End DTI

The DTI formula

Debt-to-income ratio is total monthly debt payments divided by gross monthly income, times 100. Gross means before taxes, 401(k) contributions, and health insurance come out, which is why the number looks better than your bank account feels. If you are salaried, divide your annual salary by 12. If you are paid hourly, multiply your rate by your weekly hours by 52, then divide by 12.

Lenders calculate two versions. Front-end (housing) DTI is only your housing payment divided by income. Back-end DTI adds every other recurring debt. When a loan officer says "your DTI", they almost always mean back-end.

Worked example

A household earning $78,000 a year has $6,500 of gross monthly income. Their monthly obligations: $1,650 rent, a $385 car payment, $220 in student loans, and $95 in credit card minimums. Total: $2,350.

Back-end DTI is $2,350 ÷ $6,500 = 36.2%. Front-end DTI is $1,650 ÷ $6,500 = 25.4%. They are right at the edge of the classic 36% guideline and comfortably under 28% for housing. Before hitting 43%, they have $445 a month of room ($6,500 × 0.43 − $2,350). That is the most a new car or mortgage payment could add before many lenders start to push back.

Now pay off the car. Back-end DTI drops to 30.2%, a six-point improvement from one account. That is why paying off a small loan with a big payment beats spreading the same cash across a large balance.

The thresholds lenders use

28/36 is the traditional rule: at most 28% of gross income on housing and 36% on all debt. It remains the benchmark for conventional loans with manual underwriting.

43% was the hard cap for a federal Qualified Mortgage from 2014 until the CFPB replaced it with a price-based test in 2021. Many lenders still use 43% as a practical ceiling. Fannie Mae's Selling Guide allows up to 36% for manually underwritten loans, 45% with strong credit and reserves, and 50% through its Desktop Underwriter system.

FHA's standard ratios are 31% front-end and 43% back-end, and FHA's automated approval can accept higher back-end ratios with compensating factors such as cash reserves or minimal payment shock. VA loans use 41% as a guideline but lean heavily on residual income. Auto lenders and personal loan companies vary widely, but above 45-50% approval odds drop sharply.

What counts, and what does not

Counts: the housing payment you will have (for a mortgage application, the new PITI, not your current rent), auto loans and leases, student loans, the minimum payment on each credit card, personal loans, buy-now-pay-later plans that report to credit bureaus, child support, and alimony.

Does not count: utilities, groceries, gas, cell phone, internet, car insurance, health insurance, streaming subscriptions, and 401(k) contributions. These matter for your budget but not for DTI.

Deferred student loans are a common surprise. Even if you pay $0 today, lenders usually assign a payment: often 0.5% to 1% of the balance per month depending on the loan program. A $40,000 balance can add $200 to $400 to your debt total.

Common mistakes

Using take-home pay. DTI uses gross income. Plugging in net pay makes your ratio look 20-30% worse than a lender will calculate it.

Using the credit card balance instead of the minimum. DTI counts the required minimum payment on your statement, not what you choose to pay or what you owe in total.

Forgetting co-signed loans. If you co-signed a relative's car loan, that payment usually counts against your DTI too, unless you can show 12 months of the other person paying it.

How to use your number

Before applying for a mortgage, run DTI with the new housing payment rather than your rent. The home affordability calculator works backward from these same limits to a maximum price. If you are above 43%, pay down the debts with the highest payment-to-balance ratio first, avoid new credit for a few months, and make sure every source of income with a two-year history is documented.