Debt-to-income ratio: front-end vs back-end, with worked examples

Short answer: front-end DTI divides your monthly housing payment by your gross monthly income; back-end DTI divides all your monthly debt payments, including housing, by the same income. Lenders care most about back-end DTI, and 43% is a widely used guideline ceiling.

The debt-to-income ratio is the single number that most often decides how much house a borrower can buy. It is also widely misunderstood: people use take-home pay, forget minimum card payments, or don’t realise there are two ratios.

What is front-end DTI?

Front-end DTI, sometimes called the housing ratio, measures how much of your income goes to the home:

Front-end DTI = monthly housing payment ÷ gross monthly income

The housing payment is PITI — principal, interest, property taxes, homeowners insurance — plus mortgage insurance and HOA dues where they apply.

What is back-end DTI?

Back-end DTI adds every recurring debt obligation:

Back-end DTI = (housing payment + other monthly debt payments) ÷ gross monthly income

“Other debts” means the minimum payments on your credit report — auto loans, student loans, card minimums, personal loans — plus legal obligations like child support. Living costs such as utilities, insurance on your car or groceries are not debts for DTI.

A worked example

A household earns $8,000 a month before tax.

• Proposed housing payment (PITI + PMI): $2,200
• Car loan: $450
• Student loan: $300
• Credit-card minimums: $150
• Other debts total: $900

Front-end DTI: $2,200 ÷ $8,000 = 27.5% Back-end DTI: ($2,200 + $900) ÷ $8,000 = 38.75%

At a 43% back-end limit, the maximum total debt is $8,000 × 43% = $3,440. Subtract the $900 of other debts and the household could support a housing payment of up to $2,540 — about $340 more than the example home.

What DTI limits do lenders use?

There is no single number. As guidance:

• 36% back-end is a traditional comfortable level.
• 43% back-end is a common guideline, and CalcFunnel’s calculators use it as the default ceiling.
• Higher ratios are possible on some programs and with automated underwriting approvals when the file shows compensating factors such as significant reserves, strong credit or minimal payment shock.

The CFPB’s explainer on DTI is a good plain-English reference to share with borrowers.

How to lower DTI before applying

1. Pay off small balances completely. Eliminating a $150 minimum payment lowers DTI more than paying $3,000 off a large balance whose minimum barely changes.
2. Avoid new credit. A new car loan three months before applying can cost more house than the car is worth.
3. Add a co-borrower with income and manageable debts.
4. Document all stable income — bonuses, overtime and side income with a two-year history can count.
5. Target a lower price or larger down payment to shrink the housing payment itself.

Why DTI belongs on your website

A DTI calculator gives buyers an honest pre-qualification range and gives you a lead who already understands their numbers. Pair it with an affordability calculator on your first-time-buyer page, and invite them to “email me my range”. See where to put each calculator.

Estimates only. Lenders calculate DTI from verified documents and program rules.