DTI Calculator — Check Your Mortgage Qualification Ratio

What the calculator actually adds up

The module takes seven inputs — gross monthly income, current rent, car payment, student loan, credit card minimum, other debt, and the proposed mortgage payment — and combines them in one place. Current rent is collected but never added to the debt total, because it disappears the day the new mortgage replaces it. Every other monthly obligation is summed into what the calculator calls non-housing debt, and that figure plus the proposed mortgage payment becomes total monthly debt.

Two companion figures come out of the same inputs: the calculator's maximum home payment at a 28% front-end ratio (gross income × 0.28), and its maximum home payment at a 36% back-end ratio (gross income × 0.36, minus whatever non-housing debt you already carry). The second number falls as your existing debt rises — it is the payment room your other obligations leave behind, not a fixed budget.

The status labels are one scale, applied twice

Both ratios are graded on the identical four-tier scale: 20% or under is excellent, up to 28% is good, up to 36% is borderline, and anything above 36% is high. That is a deliberate simplification. It does not vary by loan type, and there is no field on this page to tell it whether you are shopping conventional, FHA, VA or USDA — the calculator has no way to know, so it does not guess. What it gives you instead is a single, consistent yardstick you can apply to any offer and compare against your own numbers before a lender applies theirs.

That also means the 36% line is a genuinely conservative one. It is the boundary this specific tool uses to switch a back-end ratio from "borderline" to "high" — not a cutoff any single loan program publishes. Treat a "high" reading here as a flag to dig into your specific program's real limit, not as a rejection.

A worked example at the front-end cap

The same inputs also produce the calculator's 36%-based payment ceiling: $8,000 × 0.36 − $750 = $2,130. That is $110 below the $2,240 payment this borrower proposed. The front-end ratio says good; the calculator's own back-end-consistent number says the realistic room is $110/month lower. Reading both figures together, rather than either alone, is the point of running the two ratios side by side.

What isn't in this number

The "proposed mortgage" field is whatever payment you type into it. The calculator does not build that number up from a loan amount, term and rate, and it does not add estimated property tax, homeowners insurance, HOA dues or mortgage insurance on top. If you enter a bare principal-and-interest figure, both ratios understate what an underwriter will actually count — real DTI calculations are run against full PITI, not P&I alone.

It also has no concept of loan size relative to the conforming loan limit. FHFA set the 2026 baseline one-unit conforming limit at $832,750, rising to $1,249,125 in high-cost areas. A proposed mortgage payment large enough to imply a loan above that line is a jumbo loan, underwritten on its own program guidelines — a different situation than the conventional/FHA territory this tool's 36% line was chosen to approximate.

How to use this before you talk to a lender

1. Build your proposed mortgage payment honestly — principal and interest at a real rate, not a placeholder. The current benchmark is Freddie Mac's Primary Mortgage Market Survey, which put the 30-year fixed average at 6.71% for the week ending September 3, 2026 (15-year fixed 6.04% the same week).
2. Check both ratios, not just one. A front-end reading of good with a back-end reading of high means your other debts, not your target house, are the constraint — the fix is different in each case.
3. Use the 36%-based maximum payment figure as your realistic ceiling for this tool's scale, and treat the front-end 28% ceiling as a secondary check, not the binding one, whenever you carry any non-housing debt at all.