Calculator

How much house is defensible

What can this income actually support, and what is stopping it?

Most affordability calculators give you a number and no reason. This one solves the budget in closed form, then tells you which of the three constraints is the one holding the answer down — because that is the one worth doing something about.

You

Before tax, all borrowers combined.

Cards, autos, student loans, alimony.

The loan and the limits

Price ceiling on these ratios—The most the limits allow, not a recommendation

What is binding

—

—

Housing-only limit—
After other debts—

A figure a good loan officer would actually steer you toward on these inputs is nearer—. The ceiling above is what the ratios permit; it assumes nothing goes wrong.

The payment at that price

Principal & interest—
Property tax—
Insurance—
HOA—
PMI—
Total monthly housing—
Loan amount—
Loan-to-value—
What the interest rate does to the answer

What this page assumes, and where it comes from

Every field starts from a placeholder you can change. The interest rate is a round starting number, not a quote, not an average, and not tied to a date — this site publishes no rates. The tax, insurance and mortgage-insurance rates are typical orders of magnitude, not your county’s or your insurer’s.
The housing budget is the smaller of the two ratio limits. Front-end caps housing costs against gross income; back-end caps housing plus every other recurring debt payment against the same income.
Conventional PMI is modelled as ending when the SCHEDULED balance reaches 80% of the original purchase price — the point the Homeowners Protection Act lets you request cancellation. Automatic termination is 78%. Both are measured against the original value, so appreciation does not count.
Property tax is applied as a flat percentage of the purchase price. Real assessments are re-struck by the county, often after a sale, and can move sharply in the first year of ownership.
The price is solved algebraically rather than by trying candidate prices: property tax depends on price, so the equation is rearranged and solved once for each of the two PMI branches, and the self-consistent branch is kept.
Every figure this calculator produces is an illustration. It uses the published rules for amortisation and mortgage insurance, and states its assumptions on the page, but it cannot know your credit profile, your county’s tax assessment or an insurer’s pricing. Treat the shape of the answer as useful and the exact dollar as a placeholder.

Questions this raises

What are the two ratios, and which one matters?

The front-end ratio caps housing costs as a share of gross income. The back-end ratio caps ALL your monthly debt payments — housing plus cards, autos, student loans and alimony — as a share of the same income. Whichever produces the smaller housing budget is the one that decides your answer, and this page names it rather than leaving you to work it out.

Why 28% and 36%?

They are the classic conservative guideline, not a legal limit. Automated underwriting routinely approves higher back-end ratios — 45% is common and 50% happens — but a ratio a lender will accept and a payment you can live with on a bad month are different questions. Both fields are yours to change.

Why does the answer move so much when I change the rate?

Because you are borrowing against a fixed monthly budget, and the rate decides how much loan that budget buys. The chart shows the whole curve: at the same income, a few points of rate can move the supportable price by a third.

Should I actually buy at the top of this range?

The number this produces is a ceiling derived from ratios, not a recommendation. It knows nothing about your job security, your childcare costs, your car breaking down, or how much you want to save. A figure roughly fifteen percent below the ceiling is shown alongside it for that reason.

Ask a person about this

A real lender would want these five things before it could say anything useful.

This form is a demonstration. Submitting it validates your entries and shows you the confirmation state. Nothing is saved, nothing is sent, and nobody will call you. See the README for the single seam where real delivery would be wired in.

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