- A lender’s pre-approval is the maximum they’ll lend — not what you can comfortably afford. The two numbers routinely differ by $100,000+.
- The classic guardrail: housing under 28% of gross income, total debts under 36% — with your real budget built from take-home pay.
- The mortgage is only 65–80% of true ownership cost once taxes, insurance, maintenance and utilities are counted.
- Buy for the monthly payment you can sustain, not the purchase price you can reach.
Ask a lender how much house you can afford and you'll receive a number that answers a different question: how much they're willing to lend before your default risk becomes uncomfortable for them. Their ceiling and your comfortable budget are separated by everything a mortgage payment doesn't include — and by the difference between qualifying on paper and living well in practice. Here's how to compute your own number before anyone shows you houses.
Why the pre-approval overshoots
Lenders qualify you on gross income and count only debts that appear on your credit report. Your actual life runs on take-home pay and includes childcare, retirement contributions, groceries, travel and everything else that never touches a credit bureau. A household grossing $140,000 might be approved for a payment near $3,900 — while their after-tax, after-401(k), after-daycare reality comfortably supports $2,800. Both numbers are “correct.” Only one of them lets you keep saving.
The 28/36 rule — a starting guardrail
The traditional standard: housing costs (payment, taxes, insurance) below 28% of gross monthly income, and total debt payments including the house below 36%. On $140,000 gross ($11,667/month), that's a housing ceiling of about $3,270 and a total-debt ceiling of $4,200. Modern loans often approve well above these ratios — FHA can stretch past 50% total — but “can be approved” and “should sign” are different sentences. Treat 28/36 as the outer boundary and build your real number from net income.
The costs the mortgage calculator hides
The principal-and-interest figure everyone shops with is only part of the bill:
| Cost | Typical range |
|---|---|
| Property taxes | 0.5–2.5% of home value per year, varies enormously by state and county |
| Homeowners insurance | $1,200–$3,000+/yr; far more in disaster-prone regions |
| PMI (down payment under 20%) | 0.3–1.5% of loan per year until ~20% equity |
| HOA/condo fees | $0–$600+/month where applicable |
| Maintenance & repairs | Budget 1–2% of home value annually — lumpy but inevitable |
| Utilities step-up | Houses cost more to heat, cool and water than apartments |
Stack these and the true monthly cost of ownership typically runs 25–50% above the principal-and-interest number. A “$2,400 mortgage” is often a $3,300 house.
Compute your number in five steps
- Start from monthly take-home pay — after taxes and after retirement contributions you refuse to pause.
- Subtract real non-housing spending: debts, food, transport, childcare, healthcare, subscriptions, honest fun budget.
- Subtract continued saving — emergency fund maintenance and goals beyond the house.
- What remains is your all-in housing budget. Multiply by ~0.75 to get the principal-and-interest portion; that's the number to put into mortgage calculators.
- Convert to price using current rates and your down payment. Keep an emergency fund after closing — a house with no cushion is a stress machine.
Adjustments worth making
- Variable income: compute from your conservative-year income, not your best year.
- Planning kids or a career change: qualify the future budget, not the current one.
- High-property-tax states: taxes can rival the mortgage itself over time — check the actual parcel's history, not the county average.
- First home: budget a furniture-and-fixes fund for year one; nearly everyone underestimates it.
Reader questions, answered
Is 20% down still necessary?
No — conventional loans go to 3% down and FHA to 3.5%. Under 20% you'll pay PMI until you reach ~20% equity, which adds cost but can be rational when rents are high and prices rising. It's a trade-off, not a rule.
Should I stretch now since my income will grow?
Careful. Stretching assumes the raise arrives, no shocks intervene, and rates/taxes/insurance stay tame. The strained years arrive first and compound. Buying within today's means and upgrading later is the lower-regret path for most.
Renting vs buying — how do I compare honestly?
Compare rent against the full ownership cost (payment, taxes, insurance, maintenance, HOA) minus principal paydown and expected appreciation, and weigh how long you'll stay — under five years, transaction costs often make renting win outright.
Do online affordability calculators account for all this?
Most don't — they typically show principal and interest, sometimes taxes and insurance, and almost never maintenance, PMI details or your real take-home budget. Use them for the P&I conversion in step 4, not for the decision itself.