Not just a number — a clear verdict. Enter your income and debts and see the home price you can comfortably afford under the 28/36 rule, updated as you type.
Most "how much house can I afford" tools spit out one big number and leave you guessing whether it's realistic. This mortgage affordability calculator does the opposite: it shows the home price you qualify for and then tells you whether that purchase would be comfortable, tight, or a stretch based on how much of your income the payment eats up. That verdict is the part lenders quietly judge you on — and the part rival calculators hide.
It works for both the US and the UK. In the US it applies the classic 28/36 rule that underwriters use; in the UK it applies the income-multiple cap (typically around 4.5× salary) that most high-street lenders use. Either way, your monthly housing cost includes the mortgage, property tax and insurance — not just the loan payment — so the number you see is the all-in figure, the one that actually shows up in your bank account each month.
Affordability isn't about the loan you want — it's about the payment your income can carry once your other debts are counted. Lenders measure that with two ratios.
The 28/36 rule is the backbone of US mortgage underwriting:
Front-end (housing) ≤ 28% of gross monthly income
Back-end (all debt) ≤ 36% of gross monthly income
The front-end ratio says your total housing cost — mortgage principal, interest, property taxes and insurance (PITI) — should stay at or under 28% of your pre-tax monthly income. The back-end ratio adds in every other monthly debt (car loans, student loans, minimum credit-card payments) and caps the lot at 36%. Your maximum affordable payment is whichever of those two limits is lower once your existing debts are subtracted.
Once you know the maximum monthly payment you can support, you back out the home price. First, taxes and insurance are stripped out of the payment to leave the part available for principal and interest. Then the standard mortgage formula is reversed to find the largest loan that payment can service:
Loan = P&I × [1 − (1 + r)⁻ⁿ] ÷ r
where r is the monthly interest rate (annual ÷ 12) and n is the number of monthly payments (years × 12). Add your down payment to that loan and you have the maximum home price. This calculator runs that whole chain instantly every time you change a field.
UK lenders take a simpler route: they cap the mortgage at a multiple of your salary, usually 4 to 4.5×, with affordability stress-tests layered on top. Switch the toggle to UK and the calculator uses a 4.5× cap reduced by your existing debts, then adds your deposit to give the property price you could realistically offer on.
Your deposit is the biggest lever you control. The table below shows roughly how the maximum affordable price moves as the down payment changes, for a household earning $90,000 with $450/month of other debt at a 6.5% rate over 30 years (US, 28% front-end limit). Use it as a sense-check against your own result above.
| Down payment | Max loan | Max home price | Est. monthly (PITI) |
|---|---|---|---|
| $20,000 | $298,000 | $318,000 | $2,100 |
| $40,000 | $298,000 | $338,000 | $2,100 |
| $60,000 | $298,000 | $358,000 | $2,100 |
| $80,000 | $298,000 | $378,000 | $2,100 |
Notice the loan size stays the same — it's capped by your income, not your deposit. A bigger deposit raises the price you can buy, not the loan you can carry. Lowering the rate, clearing debt or earning more is what raises the loan itself.
Income $120,000, no other debt, $60,000 down, 6.5% over 30 years. The 28% front-end cap allows $2,800/month for housing. After tax and insurance that supports a loan near $380,000, giving a home price around $440,000 — and because total debt sits well under 36%, the verdict is Comfortable.
Income $75,000, $500/month car payment, $25,000 down, 7% over 30 years. The back-end ratio bites first: $500 of debt eats into the 36% cap, trimming the housing budget. The result lands a home around $260,000, but the payment uses most of the available room — verdict Tight, meaning little buffer for emergencies.
Income $60,000, $700/month in loans, small deposit, 7.5% rate. Existing debt already consumes a big slice of the 36% limit, so the qualifying payment shrinks and the affordable price falls below the buyer's target. Verdict Stretch — the honest signal to pay down debt or adjust the budget before house-hunting.
Enter your gross (pre-tax) annual income, your down payment, your total other monthly debt, the interest rate you've been quoted, the loan term and an estimate for annual property tax plus insurance as a percentage of the home's value (1.5% is a reasonable US default; UK buyers can lower it). The maximum affordable price, the all-in monthly payment and a plain-English verdict appear instantly. Try nudging the rate or your debt down to see how quickly your budget grows.
Pay down debt first. Every $100/month of debt you clear frees roughly the same room in your housing budget under the back-end ratio — often worth $15,000–$20,000 of extra home price. Shop the rate. Half a percentage point off the rate can add tens of thousands to the loan you qualify for. Lengthen the term carefully. A 30-year loan qualifies you for more than a 15-year one, but you pay far more interest over time. Grow the deposit. It won't increase your loan, but it raises the price you can reach and can knock out mortgage insurance.
A common rule of thumb is 3 to 4 times your gross annual income, but the accurate answer depends on your debts, rate and down payment. This calculator applies the 28/36 rule (US) or a 4.5× income multiple (UK) and subtracts your existing debt, then converts the qualifying payment into a home price.
It's the standard lenders use: your total housing cost should stay at or under 28% of gross monthly income (front-end ratio), and all your monthly debt combined should stay at or under 36% (back-end ratio). The lower of the two limits sets your maximum payment.
Yes. The monthly figure is PITI — principal, interest, taxes and insurance — because that's the real cost of owning. You can set the tax-and-insurance percentage to match your area; 1.5% of the home's value per year is a reasonable US default.
Your loan is capped by what your income can repay each month, not by your deposit. A larger deposit lets you buy a more expensive home (price = loan + deposit), but the loan itself only grows if you lower the rate, clear debt, extend the term or earn more.
No. It's an estimate to help you set a realistic budget before you talk to a lender. Actual approval also depends on your credit score, employment history, the property and the lender's own rules. Always confirm with a mortgage professional.
UK lenders usually cap the mortgage at around 4 to 4.5 times your salary and apply a stress test at a higher rate, rather than using the US 28/36 ratios. Switch the toggle to UK and the calculator uses a 4.5× income multiple reduced by your debts.