Home Affordability Calculator: How Much House Can I Afford?
Enter your gross monthly income, the mortgage rate and term you expect, your planned down payment, and any existing monthly debt payments. The calculator applies the standard 28/36 DTI rule to find your maximum housing payment, solves the maximum loan amount from that payment, and adds your down payment to produce a maximum home price. A side-by-side scenario table also shows how the conservative (25/36) and FHA stretch (31/43) thresholds compare.
Max home price
$376,689
Max loan
$336,689
Max monthly payment
$2,240
Front-end cap
$2,240/mo
Back-end cap
$2,880/mo
Binding constraint: Front-end (28% of income)
Max home price by DTI scenario
DTI scenario comparison
| Scenario | Max pmt | Max loan | Max price |
|---|---|---|---|
| Conservative (25/36) | $2,000 | $300,615 | $340,615 |
| Standard (28/36) | $2,240 | $336,689 | $376,689 |
| Stretch — FHA (31/43) | $2,480 | $372,763 | $412,763 |
How it works
Two debt-to-income caps determine how much housing payment a lender will approve. The front-end limit (typically 28%) caps housing costs alone at 28% of gross monthly income. The back-end limit (typically 36%) caps all monthly debts — housing plus car loans, student loans, credit cards — at 36% of income. The calculator computes both caps and takes the lower one as the binding maximum housing payment; whichever rule is tighter controls your budget.
Once the maximum monthly payment is established, the calculator solves for the largest loan whose standard principal-and-interest amortization payment equals that amount. The formula is the present-value-of-annuity inverse: loan = payment × (1 − (1 + r)⁻ⁿ) / r, where r is the monthly rate (annual rate ÷ 12) and n is the number of months. Your down payment is then added to produce the maximum home price. Note that the payment used here is P&I only; property taxes, homeowners insurance, and PMI come out of the same budget but are not explicitly modeled (see FAQ).
Three comparison scenarios are shown below your primary result: Conservative (25/36 — common for jumbo loans or cautious buyers), Standard (28/36 — the baseline used by most conventional lenders), and Stretch — FHA (31/43 — the higher limits allowed by FHA-insured loans with sufficient compensating factors). All three use the same income, debts, rate, term, and down payment you entered, so the table isolates the effect of the DTI threshold itself.
Frequently asked questions
Does the calculator include property taxes and insurance?+
The payment cap it computes is your total maximum PITI budget (principal, interest, taxes, insurance) under the DTI rule — but when solving the loan amount, the full payment is treated as P&I for simplicity. If you expect significant taxes and insurance, subtract those monthly costs from the max payment before interpreting the loan figure; for example, $300/month in taxes and $100 in insurance would reduce the effective P&I available by $400, which lowers the loan amount accordingly.
What is the 28/36 rule and where does it come from?+
The 28/36 rule is a conventional lending guideline that dates to the post-war US mortgage market and remains the baseline for most Fannie Mae and Freddie Mac conforming loans. The 28% front-end limit is meant to ensure housing costs stay manageable relative to income; the 36% back-end limit reflects the total debt load a borrower can service without undue financial stress. FHA allows 31/43, and some lenders stretch further with strong compensating factors (high down payment, large reserves, excellent credit). The limits are rules of thumb, not absolute legal ceilings.
What if the back-end cap is the binding constraint?+
When other monthly debts are high, the back-end rule bites first — reducing your available housing payment even though the 28% front-end limit alone would allow more. In that case, paying down existing debts before buying raises your maximum home price more efficiently than increasing income, because every dollar of debt eliminated directly increases the back-end room. The calculator flags which constraint is binding so you can see where the ceiling is coming from.