Front-end ratio compares the proposed monthly housing expense with qualifying gross monthly income.
Front-end ratio is the percentage of qualifying gross monthly income used for the proposed monthly housing expense. It is also called the housing expense ratio.
The front-end ratio isolates the cost of the home from the borrower’s other debts. It answers a narrow question: how large is the proposed housing obligation compared with the income the lender accepts?
This ratio can expose property-specific affordability pressure. Two homes with similar prices may produce different front-end ratios because property taxes, insurance, mortgage insurance, association dues, or assessments differ.
Not every loan program or underwriting decision gives the front-end ratio the same role. Some decisions emphasize total DTI, residual income, or automated underwriting findings. Borrowers should treat the ratio as one lens rather than a universal approval threshold.
During early qualification, the lender estimates the housing expense from an assumed loan amount, rate, taxes, insurance, and other property costs. After a property is selected, the lender uses more specific figures to build the Proposed Housing Payment.
The ratio can change before closing when the rate, purchase price, down payment, tax estimate, insurance quote, mortgage-insurance amount, association dues, or subordinate financing changes.
Here, H is proposed monthly housing expense and I is qualifying gross monthly income. The housing expense may include more than the principal-and-interest payment. The lender uses the applicable recurring property and loan costs, whether or not every item is collected through escrow.
| Component | Why it may be included |
|---|---|
| Principal and interest | Core mortgage repayment amount |
| Property taxes | Recurring ownership obligation |
| Homeowners and flood insurance | Required property coverage when applicable |
| Mortgage insurance | Required loan-level coverage when applicable |
| Association dues or assessments | Recurring property obligation for the unit or community |
| Ground rent or leasehold payment | Recurring cost on applicable leasehold property |
| Subordinate-financing payment | Additional housing-secured monthly obligation when applicable |
A lender accepts $8,000 of gross monthly income and calculates a $2,400 proposed housing expense.
If the borrower also owes $600 in counted non-housing debt, that $600 does not enter the front-end calculation. It does enter the back-end ratio.
| Ratio | Numerator | What it isolates |
|---|---|---|
| Front-end | Proposed housing expense | Housing burden only |
| Back-End Ratio | Housing expense plus other counted monthly obligations | Total recurring debt burden used in DTI |
Using the example above, the front-end ratio is 30%. Adding $600 of counted debts produces a back-end ratio of 37.5%. The same borrower and income can therefore have two different qualifying ratios.
Housing Expense is the dollar numerator. Front-end ratio converts that amount into a percentage of qualifying gross income.
Back-End Ratio adds other counted monthly debts. In common mortgage language, DTI usually refers to this broader total-debt measure.
Qualifying Payment is the mortgage payment amount required for underwriting under the product rules. Housing expense can add taxes, insurance, dues, and other applicable property charges to that amount.
Payment Shock compares a proposed payment with the borrower’s prior housing payment. Front-end ratio compares the proposed expense with income instead.