Debt-to-income calculator
Lenders do not look at what you can afford; they look at what share of your gross income is already committed. This engine computes the front-end and back-end ratios, places them against the usual 28/36/43/50 thresholds, and converts the remaining headroom into an indicative loan amount.
| Limit | Threshold | Your position |
|---|---|---|
| Front-end guideline | 28% | 25.0% · within |
| Back-end comfortable | 36% | 32.5% · within |
| Qualified mortgage | 43% | 32.5% · within |
| Typical hard ceiling | 50% | 32.5% · within |
Lenders also weigh credit score, reserves and loan-to-value; DTI alone does not decide approval.
housing / gross income · Housing cost only: principal, interest, taxes and insurance.
(housing + debt) / gross income · The number most underwriters act on.
PV(max housing payment, r/12, n) · Converts a payment ceiling into a loan amount.
A clear path from inputs to results.
Lenders do not ask what you can afford; they ask what share of your gross income is already committed. This calculator computes the front-end and back-end debt-to-income ratios, places them against the usual 28/36/43/50 thresholds, and turns the remaining headroom into an indicative loan amount.
How to use
- Enter gross monthly income, before tax.
- Enter the proposed housing payment including taxes and insurance.
- Add every other monthly debt: cards, auto, student, personal.
- Read the back-end ratio, then the payment ceiling and loan capacity.
The formula
Reference: Consumer Financial Protection Bureau qualified-mortgage standards (43% back-end); Fannie Mae and FHA underwriting guidelines.
Worked example
$8,000 a month, $2,000 housing, $600 other debt
- Gross monthly income $8,000.
- Housing payment $2,000.
- Other debt $600.
- 1
Front-end ratio: 2,000 / 8,000 = 25.0%.
- 2
Back-end ratio: (2,000 + 600) / 8,000 = 32.5%.
- 3
Payment ceiling: min(0.28 × 8,000, 0.43 × 8,000 − 600) = min(2,240, 2,840) = $2,240.
- 4
At 6.5% over 30 years, $2,240 a month supports about $354,400 of loan.
- 5
Headroom before the 43% ceiling: 3,440 − 2,600 = $840 a month.
Front-end 25.0% · back-end 32.5% · indicative capacity $354,400.
Interpreting the result
The back-end ratio is the one that decides applications, and the gap between 32.5% and the 43% ceiling is the room you have to borrow more. Notice how quickly the ratio moves with income: the same $2,600 of obligations is 32.5% at $8,000 but 26% at $10,000. That is why a raise, not a bigger down payment, often unlocks the next tier of approval.
Assumptions & limitations
- Income is gross and stable; variable, bonus or self-employed income is not haircut.
- The housing payment includes principal, interest, property tax and insurance (PITI), but not HOA dues unless you add them to other debt.
- Guideline ratios, not an approval decision — credit score, reserves and loan-to-value also apply.
- Programme limits differ: FHA, VA, USDA and jumbo loans each have their own ceilings.
Frequently asked questions
What is a good debt-to-income ratio?
Under 36% is generally comfortable, up to 43% is usually acceptable for a qualified mortgage, and above 50% is difficult without compensating factors.
Should I pay off a card or save a bigger deposit?
Clearing a monthly payment lowers the back-end ratio immediately, which can raise the loan you qualify for. The engine lets you test both by changing the debt figure.
Does rent count as debt?
Not once you are applying for the mortgage that replaces it — the new housing payment takes its place. Existing rent is not added on top.
Why is my lender’s number different?
They may include HOA dues, alimony, child support or a share of student loans, and they use their own income documentation rather than the figure you type.
Methodology last reviewed 2026-10-21. Results are informational and not financial or engineering advice — see our disclaimer.