Front-end and back-end debt-to-income ratios with lender-band gauge.
Back-end DTI is what most US lenders use for mortgages: a 36% ceiling is conventional, with 43% the regulatory cap for Qualified Mortgages.
The debt-to-income ratio (DTI) is the single number lenders watch most when deciding whether to extend a mortgage, car loan, student-loan refinance, or personal credit. It compares the sum of your recurring monthly debt obligations to your gross monthly income — and translates the resulting percentage into a band that maps directly to underwriting policy. A back-end DTI of 28 % opens the door to nearly every conventional product on offer; a back-end DTI of 45 % closes most of them and prices the rest at a premium. Borrowers routinely under-estimate their own DTI because they forget recurring obligations (student loans in deferment, child support, alimony, parking, lease payments), or because they tally net pay rather than gross pay. This calculator forces a clean accounting: gross income on one side, the full recurring-debt stack on the other, and an honest ratio in between.
DTI matters even outside borrowing decisions. It is a lagging proxy for personal-finance health: high DTI is correlated with low emergency-fund coverage, high credit-utilization, and the kind of fragility where a single missed paycheck snowballs into late fees and credit-score damage. Tracking DTI quarterly — even when you are not applying for credit — is one of the cleanest leading indicators that lifestyle creep is outpacing income growth.
Front-end DTI = housing_payment ÷ gross_monthly_income × 100 %.
The housing payment is the fully loaded PITI: principal, interest, property taxes, homeowner's insurance, and HOA dues if applicable. Renters substitute their monthly rent. Front-end DTI is the metric used for the housing-only debt burden and is what mortgage lenders look at when deciding whether you can shoulder the new mortgage you are applying for.
Back-end DTI = (housing_payment + all_other_recurring_debts) ÷ gross_monthly_income × 100 %.
The other-debts term sums every line that lenders see on your credit report or bank statement: car loan or lease payment, student-loan minimum (even if currently deferred — lenders impute it), credit-card minimum payments, personal-loan installment, court-ordered child support or alimony, co-signed loans, buy-now-pay-later instalments. Back-end DTI is the comprehensive measure and is the one that drives the band gauge in this calculator.
The four bands map to widely cited US underwriting policy: < 20 % excellent, < 36 % good, < 43 % manageable (the upper edge of Qualified Mortgage rules), ≥ 43 % poor. European lenders are typically stricter (35 % is a common ceiling for French taux d'endettement under the HCSF rules) but the band shape is similar.
Enter your gross monthly income — pre-tax, pre-deduction, all sources. Salary, freelance, rental income, alimony received, and reliable side income count; one-off bonuses and irregular income generally do not. Enter your mortgage or rent as the all-in monthly housing payment. Fill the four debt-line slots: car payment, student loans, credit-card minimums, other recurring debts. The result panel shows your back-end DTI as the headline KPI, your front-end DTI as a secondary KPI, the total monthly debt burden in your local currency, your headroom against the conventional 36 % ceiling (positive means room to add debt, negative means you are already over), and a band label. The gauge plots your back-end DTI against the four lender bands so you can see at a glance which bracket you fall in.
Two-earner household. Gross monthly income € 5 500. Mortgage € 1 500 PITI. Car payment € 350. Student loans € 200. Credit-card minimums € 80. No other debts.
The household is € 150 over the conventional 36 % ceiling. Most lenders will still extend new credit but at slightly worse pricing; large purchases (a second car, a vacation home) would push the file into the high-DTI bucket and trigger manual underwriting. Paying off the credit-card balance and freeing the € 80 minimum brings the back-end DTI to 37.3 %, just over 36 % — close enough that lenders will treat the file as a 36 %-ish prime borrower.
Gross, not net. Lenders use pre-tax income because tax burden varies by jurisdiction and filing status; they want a comparable yardstick. Plugging in net income inflates the DTI and makes you look worse than you are.
Imputed payments on deferred debt. A student loan in income-driven repayment with a $0 monthly payment is not free; lenders typically impute 0.5 % to 1 % of the balance as a notional payment for DTI purposes. If you have a deferred $40 000 loan, count $200 to $400 even though your statement says $0.
Forgotten obligations. Co-signed loans count as your debt for DTI even if a relative makes the payments. The same is true for buy-now-pay-later instalment plans, club memberships billed monthly that show on the credit file, and recurring medical-debt payments.
Income that doesn't count. One-off signing bonuses, restricted stock units that vest unevenly, gambling income, and short-tenure freelance income are usually excluded by lenders, even though you receive them every month. Use only stable income that has at least a two-year history.
Front-end vs back-end emphasis. FHA loans cap front-end at 31 % and back-end at 43 %; Fannie Mae conventional is 28 % / 36 % traditionally with overlays up to 50 % back-end for strong files. Knowing which ratio your lender weights more is essential when you negotiate file structuring.
Sole-prop and self-employed quirks. Tax-deductible business expenses lower AGI and therefore lower the income lenders see, even though cash flow is fine. Schedule-C borrowers often need to add back depreciation and other non-cash items — the calculator works on simple gross income and won't model the full self-employment add-back.
Property-tax + insurance escrow. The PITI the calculator expects is fully loaded. If you only enter principal and interest and forget the escrow part, you understate front-end DTI by 15 % to 25 % typically.
Variable-rate exposure. The calculator treats today's payment as fixed. ARMs, HELOCs, and credit-card minimums are variable; rising rates push DTI up without you changing anything. Stress-test by entering payments at +200 bps to see your cushion.