How this affordability calculator works
Lenders don't decide your budget from the house price — they start from your income and work backwards. This calculator does the same. It takes your gross monthly income, applies the debt-to-income limits for the lending rules you choose, subtracts your existing debt payments, and then finds the highest home price whose full monthly cost — principal, interest, property tax, insurance and HOA fees — still fits under that limit.
The front-end ratio caps housing costs as a share of income. The back-end ratio caps housing plus all other debts. Whichever limit is tighter sets your budget, and the result card tells you which one it was.
Affordability rules by country
United States: 28/36 and FHA
Conventional lenders traditionally look for housing costs at or below 28% of gross income and total debts at or below 36%. Automated underwriting often approves more — sometimes into the mid-40s for total debt — but stretching that far leaves little room for savings or surprises. FHA loans, designed for buyers with smaller down payments, use guideline ratios of 31% and 43%.
Canada: GDS, TDS and the stress test
Canadian lenders measure the Gross Debt Service (GDS) and Total Debt Service (TDS) ratios, generally capped at about 39% and 44%. Crucially, the payment is calculated at a stress-test rate — the greater of your contract rate plus two percentage points or 5.25% — so you'd still cope if rates rose at renewal. Select the Canada option and the calculator applies the stress test automatically.
United Kingdom: income multiples
UK lenders typically cap borrowing at around 4–4.5 times gross income, and the Bank of England limits how many loans above 4.5× each lender can issue. Your maximum price is therefore roughly your loan limit plus your deposit. Lenders still review your outgoings in detail, so treat the result as a ceiling rather than a target.
Worked example
A household earning $110,000 a year has gross monthly income of about $9,167. Under 28/36, housing can take up to $2,567 a month, and housing plus debts up to $3,300. With $500 of existing debt payments, the back-end limit allows $2,800 for housing, so the front-end limit of $2,567 is the binding one. After property tax and insurance, that supports a loan of about $316,000 at 6.25% over 25 years — or a price of roughly $375,000 with $60,000 down.
How to afford more house (safely)
- Pay off small debts first. Clearing a $300 car payment can raise your back-end capacity by tens of thousands of dollars of purchase price.
- Save a larger down payment. It adds to your budget dollar for dollar, and at 20% removes mortgage insurance.
- Compare property taxes between areas. A high-tax county can cost as much each month as a much bigger loan.
- Improve your credit score. A lower rate lets the same payment support a larger loan.