Understanding your affordability estimate
Debt-to-income (DTI) benchmarks used by US consumer agencies and conventional lenders provide context for the result. They are guidelines, not approval decisions.
| Ratio | Benchmark (CFPB / conventional practice) |
|---|---|
| Front-end (housing / gross income) | ≤ 28% — conventional comfort benchmark |
| Back-end (all debt / gross income) | ≤ 36% — conventional benchmark; the binding cap in this tool |
| Back-end up to 43% | Historical qualified-mortgage reference ceiling in the US |
| Above 43% | Generally requires compensating factors or specialized programs |
- The payment modeled here is principal and interest only. Property taxes, homeowner's insurance, PMI and HOA fees — which lenders include in the front-end ratio — would reduce the affordable loan amount.
- The estimate assumes a fixed rate for the full term and stable income. Rates, underwriting standards and DTI limits vary by lender, loan program and jurisdiction.
- A budget-based check (what payment leaves room for savings and other goals) can produce a lower, more personal ceiling than the 28/36 benchmark; a licensed adviser or housing counselor can help with a specific situation.
What is mortgage affordability?
Mortgage affordability is an estimate of the largest home purchase a household's income can conventionally support. The most widely cited benchmark is the 28/36 rule, referenced by the Consumer Financial Protection Bureau and used by conventional lenders: monthly housing costs should not exceed 28% of gross monthly income (the front-end ratio), and total monthly debt payments — housing plus car loans, student loans, card minimums and similar obligations — should not exceed 36% (the back-end ratio).
This calculator computes both caps and uses the tighter one. If existing debts are high, the 36% total-debt cap minus those debts can be lower than the 28% housing cap, and it becomes the binding constraint. The resulting maximum payment is then converted into a loan amount by inverting the amortization formula at the entered rate and term, and the down payment is added to produce the estimated maximum price.
Lender practice varies. Qualified-mortgage rules in the United States have historically referenced a 43% debt-to-income ceiling, and some programs allow more with compensating factors. Affordability by the 28/36 benchmark is deliberately conservative; it also does not test whether the payment feels manageable against a specific household's other spending.
How to use this mortgage affordability calculator
- Enter your gross (pre-tax) annual income. For joint applications, use combined income.
- Enter total existing monthly debt payments — car loans, student loans, personal loans and credit card minimums, but not rent or utilities.
- Enter the down payment you have available; it is added to the maximum loan to estimate the maximum price.
- Enter the mortgage rate you expect and the loan term in years.
- Read the estimated maximum home price, maximum loan and maximum monthly payment under the 28/36 rule.
The 28/36 affordability formula
The maximum housing payment is the smaller of 28% of gross monthly income and 36% of gross monthly income minus existing debt payments. That payment is converted into a principal by the inverted amortization formula, where r is the monthly rate and n the number of payments.
Worked example: a $90,000 income gives $7,500 gross monthly. The 28% cap is $2,100; the 36% cap minus $500 of debts is $2,200 — so $2,100 binds. At 6% over 30 years (r = 0.005, n = 360), the payment factor is about 166.79, so the maximum loan is 2,100 × 166.79 ≈ $350,260. Adding a $40,000 down payment gives an estimated maximum price of about $390,260.
Common mistakes
- Using take-home pay instead of gross income — the 28/36 rule is defined on pre-tax income.
- Omitting property taxes, insurance and HOA fees, which lenders count inside the 28% housing cap.
- Forgetting existing debts; a large car payment can make the 36% total-debt cap the binding constraint.
- Treating the maximum as a target — borrowing to the ceiling leaves no buffer for rate changes or income interruptions.
- Ignoring closing costs, which typically add 2–5% of the loan amount on top of the down payment.
常见问题
What is the 28/36 rule?
The 28/36 rule is a conventional lending guideline stating that monthly housing costs (principal, interest, taxes and insurance) should not exceed 28% of gross monthly income, and total monthly debt payments should not exceed 36%. The Consumer Financial Protection Bureau cites it as a common affordability benchmark. This calculator applies both caps and uses whichever produces the lower maximum payment.
How much house can I afford on a $90,000 salary?
Under the 28/36 rule, $90,000 of gross income supports a housing payment of up to $2,100 per month (28% of $7,500), provided existing debts do not push total obligations past 36%. At a 6% rate over 30 years, that payment supports a loan of roughly $350,000; with a $40,000 down payment, an estimated maximum price near $390,000. Taxes, insurance and fees reduce this in practice.
Why do my existing debts lower how much house I can afford?
The back-end ratio caps all debt payments at 36% of gross monthly income. Every dollar of existing monthly obligations — car loans, student loans, credit card minimums — is a dollar unavailable for a mortgage payment within that cap. When existing debts exceed 8% of gross monthly income, the back-end cap becomes stricter than the 28% housing cap and determines the result.
Is the 28/36 rule the same as what lenders approve?
No. It is a conservative screening benchmark. Actual approval depends on credit score, loan program, documented income, reserves and the full debt-to-income calculation including taxes and insurance. US qualified-mortgage rules have historically referenced DTI up to 43%, and some government-backed programs allow higher ratios with compensating factors.
Does this calculator include property taxes and insurance?
No. The maximum payment shown covers principal and interest only. Lenders include property taxes, homeowner's insurance, and where applicable PMI and HOA dues in the front-end ratio, so the loan a lender approves for the same 28% cap will be smaller than the figure shown here. Estimating those costs and subtracting them from the maximum payment gives a more realistic loan ceiling.
参考文献
- Consumer Financial Protection Bureau (CFPB). Debt-to-income ratio and mortgage affordability guidance. consumerfinance.gov.
- Consumer Financial Protection Bureau (CFPB). Ability-to-Repay and Qualified Mortgage rule (Regulation Z). consumerfinance.gov.
- US Department of Housing and Urban Development (HUD). Buying a home — housing counseling resources. hud.gov.
- Federal Reserve Board. A consumer's guide to mortgage settlement costs. federalreserve.gov.
- Fannie Mae. Selling Guide — debt-to-income ratio requirements. fanniemae.com.