This debt-to-income calculator calculates housing and total debt-to-income ratios from gross income and monthly obligations. Use the calculator above first, then read on: the worked example shows both ratios and which one binds against your targets, the sensitivity cases show why housing and other debts must be tested separately, and the troubleshooting section covers the income and debt entries that most often distort the ratios.
Contents:
- How this debt-to-income calculator works
- Worked example: $8,000 income, $2,000 housing, $800 debts
- What to enter, and what each input does
- What moves the result most
- When the result looks wrong
- Your next-steps checklist
- Limitations
- Frequently asked questions
- Sources
How this debt-to-income calculator works
DTI is two ratios, not one: housing alone, and housing plus everything else. Front-end DTI = housing ÷ gross income. Back-end DTI = (housing + other debts) ÷ gross income. Income must be above $0; zero other debt is allowed.
The tool also shows headroom under targets you choose: headroom = target % × income − the corresponding cost. Targets here are your budgeting choice, not a lender’s approval rule. A target is useful precisely because you set it: it turns an abstract ratio into a dollar figure — how much housing, or how much total debt, you can add before hitting the line you chose.
This tool makes no approval or eligibility claim, and no universal acceptance rule is asserted. Lenders calculate qualifying income and debts under program rules that differ from a household budget, so a ratio that passes your target here may still fail a lender’s calculation, and vice versa.
Worked example: $8,000 income, $2,000 housing, $800 debts
This is an illustrative example using the calculator’s own worked case, not an income statement or a lender decision. Inputs: $8,000 gross monthly income, $2,000 monthly housing cost, $800 other monthly debts, and 28% housing and 36% total targets.
Front-end DTI = $2,000 ÷ $8,000 = 25%. Back-end DTI = ($2,000 + $800) ÷ $8,000 = 35%. Against the 28% and 36% targets, housing headroom = 28% × $8,000 − $2,000 = $240 a month, and total headroom = 36% × $8,000 − $2,800 = $80 a month.
The total ratio, not housing alone, is the binding constraint here: only $80 of additional total debt fits under the total target, even though $240 of additional housing fits under the housing target. That is why the tool shows both headroom figures — a budget that checks housing alone would overstate the room available by $160 a month.
Use the Load worked example button above to reproduce this case in the form, then change one input at a time to see what drives the result.
What to enter, and what each input does
Gross monthly income. Enter income before tax, as lenders generally use gross income for DTI. Using net income would overstate both ratios, because the denominator would be smaller than the one lenders use. If income varies, use a conservative typical month rather than a best month, and expect a lender to apply its own qualifying-income rules.
Monthly housing cost. Enter principal, interest, taxes and insurance plus HOA dues (PITI + HOA) for the home you are considering. Leaving out tax, insurance or HOA understates the front-end ratio and overstates headroom by exactly the omitted amount.
Other monthly debts. Enter minimum monthly payments on cards, auto, student and personal loans, child support and similar obligations. Everyday spending — groceries, utilities, subscriptions — is not a debt payment for DTI purposes, even though it still affects what you can comfortably spend.
Your housing and total DTI targets. Enter the targets you want to test against. The 28% and 36% figures in the example are traditional planning targets, not a lender rule and not an approval. Changing a target changes headroom without changing either ratio, which is the point: the ratios describe your situation, and the targets describe your chosen limit.
What moves the result most
Starting from the worked example above, changing one input at a time gives:
| Change (one at a time) | Front-end DTI | Back-end DTI | Housing headroom | Total headroom |
|---|---|---|---|---|
| Original: $2,000 housing, $800 other debts | 25% | 35% | $240 | $80 |
| Housing up to $2,200 a month | 27.5% | 37.5% | $40 | −$120 (over target) |
| Other debts down to $400 a month | 25% | 30% | $240 | $480 |
| Income up to $9,000 a month, other inputs unchanged | 22.22% | 31.11% | $520 | $440 |
Three lessons stand out. First, housing moves both ratios, so a $200 housing increase both nearly exhausts housing headroom and pushes the total ratio over its target. Second, paying down other debts moves only the back-end ratio, which is why debt payoff helps most when the total ratio is the binding constraint — as it is in the worked example. Third, income moves both ratios and both headroom figures at once, which is why a ratio built on an overstated income figure flatters every result simultaneously.
When the result looks wrong
Both ratios look far too high. Check whether net income was entered instead of gross income, or whether a debt was entered twice — for example, a housing cost that already includes an item also counted as an other debt. Either error inflates the ratios directly.
Both ratios look far too low. Check whether housing omits tax, insurance or HOA, or whether other debts omit a loan or a card minimum. A missing debt understates the back-end ratio while leaving the front-end ratio untouched, which is a useful diagnostic: if only the back-end ratio looks wrong, the missing item is almost certainly an other debt.
Headroom is negative. That means the corresponding cost already exceeds the target you set. It is not an error: it is the tool telling you the target is already breached. Either lower the cost, raise the target deliberately (and note that you did), or accept that the scenario does not fit the target.
Your ratio passes here but a lender disagrees. That is expected. Lenders calculate qualifying income and debts under program rules that differ from a household budget — for example, how variable income, deferred student loans or business debts are treated. This tool makes no approval claim, and the lender’s calculation governs.
Your next-steps checklist
- Run this debt-to-income calculator with gross income, PITI + HOA housing, and every minimum debt payment, and note which ratio binds.
- Turn a candidate price into a monthly housing cost with the mortgage calculator, including tax, insurance, HOA and PMI, and feed that figure back in here.
- Check what price your income supports at your chosen targets with the home affordability calculator, using the same rate and monthly tax and insurance.
- Check the full monthly cost of owning, beyond PITI + HOA, with the homeownership cost calculator, including utilities and a maintenance reserve.
- Test a lower target that leaves room for groceries, utilities, transport, childcare, maintenance and savings, which DTI excludes.
- Take your income, debts and the price range from this exercise to a lender for pre-approval; only the lender’s underwriting can confirm what you can borrow.
Limitations
Lenders calculate qualifying income and debts under program rules that differ from a household budget (for example, how variable income, deferred student loans or business debts are treated). This tool makes no approval or eligibility claim and no universal acceptance rule is asserted. DTI excludes living expenses, savings, maintenance beyond the housing figure entered, credit score, employment history, reserves and program rules. Results are estimates only and are not a loan offer, pre-approval or financial advice.
Frequently asked questions
Gross or net income?
Gross (before tax), as lenders generally use gross income for DTI. Using net income would overstate both ratios.
What counts as other debts?
Minimum monthly payments on cards, auto, student and personal loans, child support and similar obligations. Everyday spending is not a debt payment for DTI purposes.
Is a lower DTI always better?
For borrowing capacity, generally yes — but a very low DTI achieved by an unsustainably cheap home is not a goal in itself. Use DTI alongside a full budget.
What is headroom, exactly?
Target % × income − the corresponding cost: how many dollars of housing (or of total debt) you could add before hitting the target you set. Negative headroom means the target is already exceeded.
Do the 28% and 36% targets guarantee approval?
No. They are traditional planning targets and your budgeting choice in this tool, not a lender rule. Program limits vary, and lenders add their own overlays, credit-score requirements and reserve requirements.
Sources
- Fannie Mae — Mortgage affordability calculator (scope reference preserved from the original page; the DTI arithmetic above is this site’s own calculation, not Fannie Mae’s).
- Consumer Financial Protection Bureau — What is a Qualified Mortgage? (ability-to-repay framework; DTI must be considered and verified, and no fixed DTI cap is asserted here).
Estimates only. Results from this calculator are not a loan offer, appraisal, engineering design, equipment selection or contractor quote.