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

What does a 32.67% back-end DTI mean?

It means that $2,450.00 of every $7,500.00 you earn before tax is already spoken for by debt — $1,800.00 of housing and $650.00 of everything else — and the other $5,050.00 is what is left for food, transport, saving and everything that is not a loan. The front-end ratio is the housing alone: $1,800.00 of $7,500.00 is 24.00%. The back-end ratio is the whole debt load: $2,450.00 of $7,500.00 is 32.67%. Both sit inside the lender lines — 28% for the front end, 36% for the back end — which is why this borrower is comfortable: the housing could rise by $300.00 before it hits the 28% line, and the total debt could rise by $250.00 before it hits the 36% line.

Three things to check before you trust the number

The two ratios answer different questions, and the tighter one sets the limit. The front-end ratio asks whether the house alone is affordable: 24.00% here, $300.00 a month below the 28% line. The back-end ratio asks whether the whole debt load is affordable: 32.67% here, $250.00 a month below the 36% line. A borrower with cheap housing and heavy car and student loans can pass the front end and fail the back end — at $6,000.00 a month of income with the same debts, the front end is 30.00% (past the 28% line) and the back end is 40.83% (past the 36% line but inside the 43% ceiling). Whichever ratio is tighter sets the limit, so work out both.

Gross income, not take-home pay. The ratios divide by the income before tax and benefit withholding — $7,500.00 here — because that is what lenders use. Divide by take-home pay instead and the ratios look worse than the lender sees them: on $6,000.00 of take-home pay the same $2,450.00 of debt is 40.83%, not 32.67%. And the debts that count are the required payments — car loans, student loans, credit-card minimums, child support, alimony — not utilities, groceries, insurance premiums or subscriptions. Lenders leave those out, which is exactly why qualifying for a payment and affording it comfortably are not the same thing.

The 43% figure is a ceiling, not the old law. The 43% back-end figure was the Qualified Mortgage DTI cap — the CFPB replaced it with a price-based standard in July 2021, so a loan can now be a Qualified Mortgage above 43% if the rate is close enough to the average prime offer rate. But 43% is still the number lenders quote: FHA loans use 43% as their standard back-end limit, and conventional underwriting typically stretches to 45% and up to 50% with compensating factors like strong credit or cash reserves. Treat 36% as the comfort line, 43% as the usual ceiling, and anything above 43% as stretched — and check the program you are actually applying for, because the ceiling moves with it.

Worked example

On the defaults: $7,500 a month gross, $1,800 housing, $650 other debts.

1. The total debt: $1,800 + $650 is $2,450.00.
2. The front-end DTI: $1,800 ÷ $7,500 × 100 is 24.00%.
3. The back-end DTI: $2,450 ÷ $7,500 × 100 is 32.67%.
4. The max housing at 28%: $7,500 × 28% is $2,100.00.
5. The max total debt at 36%: $7,500 × 36% is $2,700.00.
6. The max other debt at 36%: $2,700 − $1,800 is $900.00.

And the other way: the income needed for a 36% back-end DTI with $2,450.00 of debt is $6,805.56 a month, the max housing payment at the 28% line is $2,100.00 a month, and the max other debt at the 36% line is $900.00 a month.

Every branch, checked

• $6,000 a month income instead of $7,500: $6,000 a month income instead of $7,500: Front-end 30.00% ($1,800.00 of $6,000.00) — back-end 40.83% ($2,450.00 of $6,000.00). Max housing at 28% is $1,680.00; max other debt at 36% is $360.00.
• $9,000 a month income instead of $7,500: $9,000 a month income instead of $7,500: Front-end 20.00% ($1,800.00 of $9,000.00) — back-end 27.22% ($2,450.00 of $9,000.00). Max housing at 28% is $2,520.00; max other debt at 36% is $1,440.00.
• $2,100 housing instead of $1,800: $2,100 housing instead of $1,800: Front-end 28.00% ($2,100.00 of $7,500.00) — back-end 36.67% ($2,750.00 of $7,500.00). Max housing at 28% is $2,100.00; max other debt at 36% is $600.00.
• $2,400 housing instead of $1,800: $2,400 housing instead of $1,800: Front-end 32.00% ($2,400.00 of $7,500.00) — back-end 40.67% ($3,050.00 of $7,500.00). Max housing at 28% is $2,100.00; max other debt at 36% is $300.00.
• $0 other debts instead of $650: $0 other debts instead of $650: Front-end 24.00% ($1,800.00 of $7,500.00) — back-end 24.00% ($1,800.00 of $7,500.00). Max housing at 28% is $2,100.00; max other debt at 36% is $900.00.
• $1,200 other debts instead of $650: $1,200 other debts instead of $650: Front-end 24.00% ($1,800.00 of $7,500.00) — back-end 40.00% ($3,000.00 of $7,500.00). Max housing at 28% is $2,100.00; max other debt at 36% is $900.00.
• $1,500 housing instead of $1,800: $1,500 housing instead of $1,800: Front-end 20.00% ($1,500.00 of $7,500.00) — back-end 28.67% ($2,150.00 of $7,500.00). Max housing at 28% is $2,100.00; max other debt at 36% is $1,200.00.
• $400 other debts instead of $650: $400 other debts instead of $650: Front-end 24.00% ($1,800.00 of $7,500.00) — back-end 29.33% ($2,200.00 of $7,500.00). Max housing at 28% is $2,100.00; max other debt at 36% is $900.00.

The reverses, worked backwards

• Income needed for a 36% back-end DTI: $6,805.56 a month — at $6,805.56 a month the figures are Front-end 26.45% ($1,800.00 of $6,805.56) — back-end 36.00% ($2,450.00 of $6,805.56). Max housing at 28% is $1,905.56; max other debt at 36% is $650.00.; at the lower neighbor the figures are Front-end 26.45% ($1,800.00 of $6,804.56) — back-end 36.01% ($2,450.00 of $6,804.56). Max housing at 28% is $1,905.28; max other debt at 36% is $649.64.; at the upper neighbor the figures are Front-end 26.45% ($1,800.00 of $6,806.56) — back-end 35.99% ($2,450.00 of $6,806.56). Max housing at 28% is $1,905.84; max other debt at 36% is $650.36. — verdict: STEP.
• Max housing payment at the 28% line: $2,100.00 a month — at $2,100.00 a month the figures are Front-end 28.00% ($2,100.00 of $7,500.00) — back-end 36.67% ($2,750.00 of $7,500.00). Max housing at 28% is $2,100.00; max other debt at 36% is $600.00.; at the lower neighbor the figures are Front-end 27.99% ($2,099.00 of $7,500.00) — back-end 36.65% ($2,749.00 of $7,500.00). Max housing at 28% is $2,100.00; max other debt at 36% is $601.00.; at the upper neighbor the figures are Front-end 28.01% ($2,101.00 of $7,500.00) — back-end 36.68% ($2,751.00 of $7,500.00). Max housing at 28% is $2,100.00; max other debt at 36% is $599.00. — verdict: STEP.
• Max other debt at the 36% line: $900.00 a month — at $900.00 a month the figures are Front-end 24.00% ($1,800.00 of $7,500.00) — back-end 36.00% ($2,700.00 of $7,500.00). Max housing at 28% is $2,100.00; max other debt at 36% is $900.00.; at the lower neighbor the figures are Front-end 24.00% ($1,800.00 of $7,500.00) — back-end 35.99% ($2,699.00 of $7,500.00). Max housing at 28% is $2,100.00; max other debt at 36% is $900.00.; at the upper neighbor the figures are Front-end 24.00% ($1,800.00 of $7,500.00) — back-end 36.01% ($2,701.00 of $7,500.00). Max housing at 28% is $2,100.00; max other debt at 36% is $900.00. — verdict: STEP.

What the defaults assume

The defaults are $7,500 a month of gross income, a $1,800 housing payment and $650 of other monthly debts. Gross means before tax and benefit withholding — the income lenders use, not take-home pay. The housing payment is the full monthly cost of the home: principal, interest, property tax, homeowners insurance and HOA dues, and the proposed payment if you are buying rather than the one you pay now. The other debts are the required monthly payments — car loans, student loans, credit-card minimums, personal loans, child support and alimony — not utilities, groceries, subscriptions or insurance premiums other than the homeowners insurance inside the housing payment. The 28/36 rule is the classic guideline, not a legal cutoff: lenders regularly approve loans above 36% back-end with compensating factors, and the 43% figure is the former Qualified Mortgage cap, replaced by a price-based test in July 2021, still used as a lender ceiling. The income reverse is checked at $1 either side, because a $1 change in a $6,805.56 income moves the back-end ratio by about 0.01 points; the max-housing and max-other reverses are exact whole-dollar figures at the 28% and 36% lines. The model does not count the debts lenders leave out, and it does not judge whether the remaining income is enough to live on — that is a budget question, not a ratio.

These notes repeat in every explainer section because this page is built to be read start to finish: the two ratios answer different questions, and the tighter one sets the limit; gross income, not take-home pay; and the 43% figure is a ceiling, not the old law.

Output · formula · meaning

Who uses this

• A homebuyer checking the max payment — on $7,500.00 a month gross, the housing payment can rise to $2,100.00 before it hits the 28% line: the ceiling, before the house hunt starts.
• A borrower weighing a car loan against a mortgage — $650.00 of other debts leaves $900.00 of room at the 36% line: the car payment that fits, and the one that breaks the mortgage.
• A homeowner deciding whether to refinance — the front end is 24.00% and the back end 32.67%: both inside the lines, so the refinance is a rate question, not a qualification question.
• A student learning lender math — one worked example from gross income to front-end to back-end to the max payments, and the branches that show how income, housing and other debts each move the ratios.

Accuracy & limitations

Figures are the model's own ratios on the numbers you type, computed from unrounded values: the front-end ratio is the housing payment divided by gross monthly income times 100, the back-end ratio is the housing plus other debts divided by gross monthly income times 100, the max housing is the income times 28%, the max total debt is the income times 36%, and the max other debt is the max total debt minus the housing payment. The displayed figures are rounded to 2dp. The income reverse is the smallest whole-cent income that brings the back-end ratio to 36% — $6,805.56 — checked at $1 either side. The 28/36 rule is a guideline: lenders use program-specific limits (conventional up to 45–50% back-end with compensating factors, FHA 43% standard, VA 41% guideline with residual income), and the 43% Qualified Mortgage cap was replaced by a price-based test in July 2021. The model counts only the debts lenders count, and it does not check credit score, down payment, cash reserves or employment history — all of which the underwriter weighs alongside the ratios. This page is a calculation tool, not financial advice, and not a mortgage pre-approval.

Cite this calculator

On $7,500 a month gross with $1,800 housing and $650 other debts, the front-end debt-to-income ratio is 24.00% and the back-end is 32.67% — inside both lender lines (28% and 36%). The 28/36 rule: front-end at or under 28%, back-end at or under 36%; the 43% figure was the former Qualified Mortgage cap (CFPB, replaced July 2021) and is still used as a lender ceiling. Source: Bright Side Kit, brightoolbox.com.

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