Front-end vs. back-end DTI
Fannie Mae and other conforming loan guidelines commonly reference two versions of DTI. The front-end ratio covers only the proposed housing payment — principal, interest, property taxes, insurance and any HOA dues. The back-end ratio covers the housing payment plus all other recurring debt obligations, such as car loans, student loans, minimum credit card payments and other installment debt. Lenders generally weigh the back-end ratio more heavily for mortgage qualification, since it captures a fuller picture of a borrower's existing debt load.
DTI is calculated using gross (pre-tax) monthly income, not take-home pay — the standard convention in mortgage underwriting. It also does not consider household expenses outside formal debt payments, such as groceries, utilities, or childcare, so a low DTI does not by itself guarantee comfortable monthly cash flow.
- Front-end DTI = (housing payment ÷ gross monthly income) × 100
- Back-end DTI = ((housing payment + other monthly debts) ÷ gross monthly income) × 100
Worked example
A household with $6,000 in gross monthly income, a $1,500 housing payment and $600 in other monthly debts has a front-end ratio of 25% ($1,500 ÷ $6,000) and a back-end ratio of 35% (($1,500 + $600) ÷ $6,000) — total monthly obligations of $2,100.
The 28/36 rule and what lenders actually allow
The commonly cited 28/36 rule — a front-end ceiling of 28% and a back-end ceiling of 36% — originated as a conventional mortgage-underwriting guideline. Many lenders today, particularly for conforming loans, permit back-end DTI up to 43% or higher with strong compensating factors such as a high credit score or large cash reserves, so the 28/36 figures are best read as a conservative benchmark rather than a universal cutoff. Government-backed programs such as FHA loans have historically permitted higher back-end DTI ratios than many conventional loans.
| Back-end DTI | Classification | Typical lending context |
|---|---|---|
| 36% or below | Healthy | Within the conventional 28/36 back-end guideline |
| 36.01% – 43% | Manageable | Above the conventional guideline but within common conforming-loan ceilings |
| 43.01% – 50% | Stretched | Above typical conforming ceilings; usually requires compensating factors |
| Above 50% | High | Exceeds most conventional lending ceilings |
What counts as debt — and common mistakes
DTI counts recurring debt obligations with a fixed monthly payment: the housing payment, car loans, student loans, minimum credit card payments, personal loans and similar debt. It does not include everyday living expenses such as groceries, utilities or subscriptions. Two common errors distort the ratio: using net (take-home) income instead of gross income understates DTI relative to how lenders compute it, and omitting part of the housing payment — such as property taxes or HOA dues — understates both ratios.
Frequently asked questions
What is a good debt-to-income ratio?
The widely cited 28/36 guideline treats a front-end ratio at or below 28% and a back-end ratio at or below 36% as a conservative benchmark. Many lenders permit back-end DTI up to 43% or somewhat higher for conforming loans with strong compensating factors.
What counts as debt in a DTI calculation?
Recurring obligations with a fixed monthly payment: the housing payment (principal, interest, taxes, insurance, HOA), car loans, student loans, minimum credit card payments and similar installment or revolving debt. Everyday living expenses like groceries and utilities are not included.
Does DTI use gross or net income?
Gross (pre-tax) monthly income, not take-home pay. This is the standard mortgage-underwriting convention, so using net income instead produces a DTI figure that won't match how a lender calculates it.
Can I get a mortgage with a DTI above 36%?
Often, yes. Many conforming loan programs permit back-end DTI up to 43% or higher with compensating factors such as a high credit score, larger down payment, or substantial cash reserves, and government-backed programs like FHA have historically allowed higher ratios than many conventional loans.
References
- Consumer Financial Protection Bureau (CFPB) — What is a debt-to-income ratio? https://www.consumerfinance.gov/
- Fannie Mae. Selling Guide — B3-6-02: Debt-to-Income Ratios. https://www.fanniemae.com/
- U.S. Department of Housing and Urban Development (HUD) — FHA underwriting guidelines. https://www.hud.gov/