Mortgage Affordability Calculator
The most expensive home you qualify for, worked out the way a Canadian lender does. GDS and TDS ratios, the stress test, and your down payment's own ceiling.
Rates & rules verified · July 2026Primary sources: OSFI – Guideline B-20 (mortgage underwriting) · FCAC – Down payment requirements · CMHC – Mortgage loan insurance
What more income or savings buys
Maximum home price as income (across) and down payment (down) change, with debts, rate, property tax, heat and condo fees held at your figures.
Where your monthly budget goes
Lenders start from 39% of your gross monthly income, take off other debts past the 44% total-debt limit, then property tax, heat and half of any condo fees. What is left is the most your mortgage payment can be at the stress-test rate.
Your ratios at the maximum price
How rates move your budget
Maximum purchase price at contract rates two points either side of yours, everything else held constant. The stress test amplifies every move.
Price by down payment
What you could buy at different down-payment shares of the resulting price. More down means less CMHC, and from 20% no insurance at all.
| Down share | Down $ | Max price | Mortgage | CMHC | Payment/mo |
|---|
How this is calculated
The two ratios lenders use
Every Canadian lender runs your numbers through two debt-service tests and takes the lower result:
GDS (Gross Debt Service), max 39%. Housing costs only: GDS budget = income ÷ 12 × 0.39. Housing = mortgage payment + property tax + heat + ½ of condo fees.
TDS (Total Debt Service), max 44%. Housing plus every other debt payment: TDS budget = income ÷ 12 × 0.44 − monthly debts.
Your money available for principal & interest is min(GDS, TDS) − tax ÷ 12 − heat − 0.5 × condo. Whichever ratio produces the smaller housing budget is the one that binds, the calculator names it in the verdict box.
The stress test (why qualifying ≠ contract)
OSFI B-20 requires lenders to test you at the qualifying rate, the greater of your contract rate + 2% or 5.25%. The maximum mortgage is solved from the qualifying payment, so the mortgage you can borrow is smaller than a naïve calculator at your contract rate would suggest. The monthly payment shown in the metrics is then re-computed on that mortgage at your real contract rate, which is why it's lower than the qualifying payment you were tested against.
Solving for the loan
Given the available payment pay, the maximum loan is the present value of that payment stream: L = pay × (1 − (1 + r)⁻ⁿ) ÷ r, where n is amortization in months and r = (1 + qualifying ÷ 2)^(2/12) − 1, the effective monthly rate from Canada's semi-annual compounding.
CMHC and the down payment ceiling
Below 20% down, default insurance is mandatory and its premium (0.60%–4.00% of the loan, +0.20% for an insured 30-year amortization for first-time buyers and new builds) is added to the mortgage. Because the premium depends on the loan-to-value, which depends on the price, the calculator solves each premium tier exactly: inside a tier the premium is flat, so price = down + capacity ÷ (1 + premium), and if that lands past the tier's edge the price stops at the edge, where the next tier's premium would break the budget. Two hard ceilings can override your income: the minimum down payment (5% of the first $500,000, 10% above, 20% at $1.5M+) and the rule that insured mortgages are unavailable at $1.5M or more. A non-first-time buyer (and non-new-build) with less than 20% down is limited to a 25-year amortization, so choosing 30 years does not raise their budget, toggle First-time buyer or new build if it applies (rule in force December 15, 2024).
Insured or uninsured: the calculator tries both
It works out two purchases and shows the larger one that is legal and fits your ratios. Insured: under 20% down, a price below $1.5M (at most $1,499,999), at least the minimum down payment, the premium financed on top. Uninsured: at least 20% down (price ≤ down ÷ 0.20), no premium, and the amortization you chose, since the 25-year cap applies only to insured loans. So a large income with $200,000 down buys just under $1.5M insured, rather than the $1,000,000 that 20% down covers, and a buyer whose premium would break the budget can still buy at exactly 20% down. The verdict box names whichever limit binds: GDS, TDS, the minimum down payment, 20% down, or the $1.5M insured cap.
The charts
What more income or savings buys re-runs the full calculation for each cell, with incomes in steps of about 15% of yours and down payments in steps of about 25% of yours (rounded to $5,000), holding debts, rate, property tax, heat and condo fees at your figures. The outlined cell is your result and equals the headline price. An asterisk marks cells where the down payment rules, not income, set the price.
Where your monthly budget goes starts at income ÷ 12 × 0.39, subtracts other debts only where they push past the 44% TDS limit (min(0, TDS room − GDS room)), then property tax ÷ 12, heat and half the condo fees. The last bar is the payment left for principal and interest at the stress-test rate, never below $0. The ratio bars show GDS and TDS for the mortgage at your maximum price: the bar at your contract rate (what you would actually carry), the tick as tested at the qualifying rate, which sits at the 39% or 44% limit whenever income is what binds.
How rates move your budget repeats the whole calculation at contract rates in half-point steps two points either side of yours. At 3.25% and below the qualifying rate is the 5.25% floor rather than contract + 2%, so those bars stop rising.
What this doesn't model
Land transfer tax, closing costs, lender-specific overlays, self-employment income adjustments, or credit-score pricing. Property tax defaults to a flat $4,000 rather than a percentage of the (unknown) price. Pair this with the mortgage payment calculator, land transfer tax calculator, and rent vs. buy calculator for the full picture. Rules and tiers confirmed as of July 2026 (OSFI B-20, CMHC, FCAC).
Common questions
How do Canadian lenders decide how much mortgage I can afford?
Lenders apply two debt-service ratios. Gross Debt Service (GDS) caps your housing costs, mortgage payment, property tax, heat, and half of condo fees, at 39% of gross income. Total Debt Service (TDS) caps housing plus all other debt payments at 44%. Your budget is the lower of the two, and the mortgage payment is tested at the stress-test rate, not your contract rate.
What is the mortgage stress test in 2026 and how does it affect affordability?
Under OSFI B-20 you must qualify at the greater of your contract rate plus 2% or 5.25%. With a 4.44% contract rate you qualify at 6.44%. Because the qualifying payment is higher than what you actually pay, the stress test lowers the maximum mortgage you can borrow even though your real payment is smaller.
Does my down payment limit how much house I can buy?
Yes. Canada requires a minimum of 5% down on the first $500,000 and 10% on the portion above, and 20% on homes of $1.5M or more. Mortgage default insurance is only available below 20% down and below the $1.5M price. If your saved down payment is small, the minimum-down-payment rule can cap your price below what your income alone would allow.
Why is the payment I qualify for higher than the payment I actually make?
The stress test qualifies you at a higher rate (contract + 2% or 5.25%). The maximum mortgage is solved from that inflated qualifying payment, but your real monthly payment on that same mortgage is calculated at your lower contract rate, so the payment you actually make is smaller than the one you were tested against.
How is CMHC insurance handled in the affordability calculation?
If you put down less than 20%, mortgage default insurance is required and its premium (0.60% to 4.00% of the loan by loan-to-value, plus 0.20% for an insured 30-year amortization) is added to the mortgage. This calculator solves for the maximum insured mortgage your qualifying payment supports, then works backward to the purchase price.