"How much house can I afford" has two different answers: how much a lender will approve you to borrow, and how much you can comfortably afford given your full financial picture. Those two numbers are often not the same, and confusing them is one of the most common ways buyers end up house-poor — approved for a loan that is technically qualifying but that leaves little room in the monthly budget for anything else.
Start with lender qualification limits
Lenders primarily use your debt-to-income ratio to decide how much you can borrow — your total monthly debt payments, including the new mortgage, divided by your gross monthly income. Each loan program sets its own maximum DTI, and lenders also weigh your credit score, down payment size, and cash reserves. See our debt-to-income ratio guide for the full calculation and how it drives your maximum approved loan amount. This number is a ceiling, not a target.
Common affordability rules of thumb
Several simplified guidelines exist to sanity-check affordability before running detailed numbers, such as keeping total housing costs under roughly a third of gross income, or keeping the purchase price within a small multiple of annual income. These rules are useful starting points, but they ignore your specific debt load, local tax and insurance costs, and personal savings goals, so treat them as a rough filter rather than a precise answer — the detailed calculation below gets much closer to your real number.
The full monthly housing payment
Affordability should be measured against your full monthly housing payment, not just principal and interest. That means including:
- Principal and interest on the loan
- Property taxes
- Homeowners insurance
- Mortgage insurance, if your down payment is below the threshold that requires it
- HOA dues, if applicable
These are commonly bundled as PITI (principal, interest, taxes, insurance). The mortgage calculator calculates all of these together so you can see the real monthly number for a given home price, not just the loan payment in isolation.
Down payment size changes the whole equation
A larger down payment reduces your loan amount, which lowers your monthly payment and may eliminate the need for mortgage insurance, but it also ties up more cash and reduces the reserves you have left after closing. A smaller down payment preserves cash but increases your monthly payment and total borrowing cost. There is no universally correct balance — it depends on your other financial goals, how much you value liquidity, and how the resulting payment fits your budget. Use the calculator to compare a few down payment levels side by side before deciding.
Don't forget the costs outside the mortgage payment
Affordability does not stop at PITI. Ongoing maintenance, utilities that may be higher than a previous rental, and the cash needed for move-in and furnishing all affect whether a home is truly affordable, not just whether the mortgage payment fits your budget on paper. Many buyers also underestimate the cash required at closing — see our closing costs guide for what to budget beyond the down payment itself.
A practical process for finding your number
Rather than relying on a single rule of thumb, work through it in order: calculate your current monthly debt obligations, estimate a comfortable maximum total housing payment given your income and other financial goals (which may be lower than what a lender would approve), use the calculator to find what home price produces that payment at a realistic rate and down payment, then add your down payment plus estimated closing costs to see your total cash requirement. Comparing that result against your actual savings tells you whether the number is realistic today or something to work toward.
Revisit the numbers before you shop
Interest rates, property tax rates, and insurance costs vary by location and change over time, so treat any affordability estimate as a starting range to refine with current, local numbers and an actual lender pre-approval — not a fixed figure to lock in months before you are ready to buy. Our first-time buyer checklist covers the pre-approval process in more detail.