How Much House Can You Afford?
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Most conventional lenders cap total monthly debt, including the new mortgage, at around 36-43% of gross monthly income, with some allowing higher ratios for strong applicants. On $8,000 gross monthly income with $400 in other debt and a 43% cap, that is roughly $3,040 available for housing costs.
Affordability is not one number. Lenders calculate a maximum based on debt-to-income ratios, but the amount you can comfortably spend depends on your own budget, savings goals and risk tolerance, which a lender does not see.
Key takeaways
- Lenders use two ratios: front-end (housing costs only) and back-end (all debt including housing).
- A common front-end guideline is 28% of gross income; a common back-end cap is 36-43%, higher for some loan programs.
- The maximum you qualify for is not the same as the amount that fits your actual budget.
- Cash reserves, other savings goals and job stability matter just as much as the ratio math.
Run the numbers with the Home Affordability Calculator.
The two ratios lenders use
- Front-end ratio (housing ratio) — proposed monthly housing payment (principal, interest, taxes, insurance, HOA) divided by gross monthly income. A common guideline is around 28%.
- Back-end ratio (total debt ratio) — housing payment plus all other monthly debt (auto loans, student loans, minimum credit card payments) divided by gross monthly income. Conventional loans commonly cap this near 36-45% depending on credit profile and compensating factors; FHA loans allow higher ratios in many cases.
Worked example
Assume gross monthly income of $8,000, existing monthly debt payments of $400 (a car loan and a credit card minimum), and a lender back-end cap of 43%.
- Maximum total monthly debt allowed: 8,000 x 0.43 = $3,440.
- Subtract existing debt: 3,440 - 400 = $3,040 available for the full housing payment (PITI).
- Estimate taxes, insurance and any HOA — assume $500 combined — leaving 3,040 - 500 = $2,540 for principal and interest.
- At 6.5% over 30 years, a $2,540 P&I payment supports a loan of roughly $402,000 (working the amortization formula backward).
- Add the planned down payment to the supportable loan amount to estimate the maximum purchase price.
Why 'maximum approved' and 'what you should spend' differ
A lender's ratio calculation does not know about your retirement contributions, childcare costs, irregular income, other savings goals, or how much risk you are comfortable carrying. Two households with identical income and debt ratios can have very different real financial flexibility.
A common practical approach is to calculate the lender maximum, then independently build a monthly budget including all recurring costs, and use whichever number is lower.
Other factors that affect the real number
- Credit score — affects both approval and the interest rate offered, which changes the payment for the same loan amount.
- Down payment size — a larger down payment lowers the loan amount and may remove the need for mortgage insurance.
- Loan program — FHA, VA, USDA and conventional loans use different ratio limits and mortgage insurance rules.
- Cash reserves required — many lenders want to see a certain number of months of payments left in savings after closing.
- Variable or irregular income — commission, bonus or self-employment income is often averaged over two years and documented more heavily.
Common mistakes
- Treating the maximum approved loan amount as a target rather than a ceiling.
- Forgetting to budget for maintenance, utilities and moving costs on top of the mortgage payment.
- Using a rate quote from months ago instead of a current one, which can shift the qualifying loan amount significantly.
- Ignoring HOA dues, which count as debt in affordability calculations but are easy to overlook when browsing listings.
A second example: tighter budget, more existing debt
Affordability changes quickly with debt load. Compare the earlier $8,000-income example against a household with the same income but $1,100 in existing monthly debt (a car payment and student loans) and a more conservative 36% back-end cap instead of 43%.
- Maximum total monthly debt allowed: 8,000 x 0.36 = $2,880.
- Subtract existing debt: 2,880 - 1,100 = $1,780 available for the full housing payment.
- Assume $450 combined for taxes, insurance and HOA, leaving 1,780 - 450 = $1,330 for principal and interest.
- At 6.5% over 30 years, $1,330 in P&I supports a loan of roughly $210,000 — well under half of the first example's supportable loan, purely from higher existing debt and a lower ratio cap.
Comparing ratio caps side by side
The back-end cap a lender applies has a large effect on the housing budget it produces. The table below holds income and existing debt constant and only changes the cap.
Housing budget at $8,000 gross monthly income and $400 existing debt
| Back-end cap | Total debt allowed | Available for housing (PITI) |
|---|---|---|
| 36% | $2,880 | $2,480 |
| 43% | $3,440 | $3,040 |
| 45% | $3,600 | $3,200 |
Frequently asked questions
What debt-to-income ratio do lenders usually require?
Conventional loans commonly allow a back-end ratio up to roughly 45% for well-qualified borrowers, though 36% is a widely cited comfortable benchmark. FHA and other government-backed programs sometimes allow higher ratios. The exact limit depends on the lender, loan program and your overall credit profile.
Does rent I currently pay count against my debt ratio?
No. Current rent is not a debt obligation in the traditional sense and is not included in the debt-to-income calculation, since it will end once you buy. Only installment and revolving debt payments, and the new proposed housing payment, are counted.
Should I spend up to my maximum approved amount?
Not necessarily. The approved maximum reflects a lender's risk tolerance, not your personal budget. Many buyers choose a purchase price below their maximum to preserve savings, flexibility and a cushion for maintenance and emergencies.
How does a down payment change what I can afford?
A larger down payment reduces the loan amount needed for the same purchase price, which lowers the monthly principal-and-interest payment and can eliminate mortgage insurance, both of which increase the purchase price you can support within the same debt ratio.
Does a bonus or overtime income count toward affordability?
Sometimes, but lenders typically want a history of at least two years and evidence the income is likely to continue, and they often average it over that period rather than counting the most recent, highest figure. One strong bonus year usually is not enough on its own.
How much do property taxes and insurance change my affordability number?
Significantly. Because they are part of the front-end housing payment used in the ratio, a high local tax rate or an expensive insurance market can reduce the loan amount a given income supports by tens of thousands of dollars compared with a lower-cost area, even at the same price and rate.
What is a compensating factor in mortgage approval?
A compensating factor is a strength in your file — such as a large down payment, significant cash reserves, a long history in the same job, or a very high credit score — that a lender may weigh to approve a loan with a debt-to-income ratio above its usual guideline.
Sources and references
- CFPB — How much can I afford? — Guidance on budgeting for total monthly housing costs, not just principal and interest.
- Fannie Mae Selling Guide — B3-6-02 Debt-to-Income Ratios — Conventional underwriting DTI limits behind the 43%-50% thresholds used here.
- HUD — FHA Single Family Housing Policy Handbook 4000.1 — FHA qualifying ratios and mortgage insurance rules for lower down payments.