See your real ceiling before you shop
Mortgage affordability calculator
Enter your income, debts and rate. This runs the same GDS and TDS ratios a federally regulated lender applies, tested at your contract rate plus two points or 5.25%, whichever is higher.
What this calculator does
It runs the same two-ratio math a federally regulated lender runs, using the income, debts, rate and amortization you enter, and reports the largest mortgage those ratios support at the stress-test rate.
The stress test is the part buyers usually miss. You are not qualified at the rate you will pay. You are qualified at the higher of your contract rate plus two percentage points, or 5.25%, and that tested rate is what decides how much the bank will lend, not your actual payment.
Use the result to set a realistic search range before you start viewing homes, not as a substitute for a lender's pre-approval on your actual file.
The two ratios that set your ceiling
Gross debt service, or GDS, caps your housing costs at 39% of gross income. Housing costs here means the mortgage payment at the tested rate, property tax, heating, and half of any strata fee.
Total debt service, or TDS, caps housing costs plus every other monthly debt payment at 44% of gross income. A car loan, a line of credit balance, or minimum credit card payments all count here at their required minimum payment, whether or not you plan to pay more.
Your maximum mortgage comes from whichever ratio produces the smaller number. For most buyers with little other debt, GDS is the binding constraint. For buyers carrying car payments or credit lines, TDS usually binds first.
- GDS limit: 39% of gross income, covering payment, tax, heat, half strata
- TDS limit: 44% of gross income, covering everything in GDS plus other debts
- The smaller of the two numbers is your real ceiling
Numbers worth entering carefully
Property tax and heat are easy to underestimate before you have a specific address. In Coquitlam and Port Coquitlam, a rough property tax estimate is a small percentage of the home's assessed value per year; check a specific property's actual tax once you have one in mind, since it varies by assessed value and can be looked up on BC Assessment.
Other monthly debt should include the required minimum payment on every revolving balance you carry, not what you intend to pay. A lender counts a credit line at its minimum payment even if you plan to pay it off in full every month.
Down payment does not change your maximum mortgage. It changes your maximum purchase price, by adding directly on top of what the bank will lend.
Frequently asked questions
What rate does this calculator use to qualify me?
The higher of your contract rate plus two percentage points, or 5.25%. That is the OSFI Guideline B-20 stress test every federally regulated lender applies. A 4.6% contract rate is tested at 6.6%, because 6.6% is higher than 5.25%. A 2.9% contract rate is tested at 5.25%, the floor, because 4.9% would be lower than it.
What are GDS and TDS?
Gross debt service (GDS) is your housing costs, meaning the mortgage payment at the tested rate, property tax, heat, and half of any strata fee, as a share of your gross income. The limit is 39%. Total debt service (TDS) adds every other monthly debt payment on top, with a limit of 44%. Your maximum mortgage is set by whichever of the two produces the smaller number.
Why is my result lower than what I could actually make the payments on?
Because the calculator tests you at the stress-test rate, not your contract rate. You will make payments at your real rate, which is usually lower, but the lender has to confirm you could still make them at the higher tested rate before approving the loan. This gap is intentional and applies to every federally regulated lender in Canada.
Does a bigger down payment increase my maximum mortgage?
No. Your down payment adds directly to your maximum purchase price, but it does not change the maximum mortgage the bank will lend, because that figure comes from your income and debts against the GDS and TDS limits. A larger down payment buys a more expensive home by reducing how much of the price needs to be borrowed, not by raising what you qualify to borrow.
Why do I need to enter property tax and heat before I have chosen a home?
Because the lender includes them in the GDS calculation regardless of which specific home you buy. Use an estimate: BC property tax generally runs a small percentage of assessed value per year, and heat is commonly estimated near $100 to $150 a month for a typical home. Once you have a specific property, its actual tax and any strata fee replace the estimate and the number will move.
Is this the amount a lender will actually approve me for?
No. This runs the same two ratios a lender uses, with the numbers you supply, but a real application also checks your credit history, employment, the source of your down payment, and the specific property's appraisal. Use this to set a realistic search range before you apply, then confirm the real number with a mortgage broker or lender.
What if I am buying with someone else?
Enter your combined gross income and your combined other monthly debts. Both incomes and both sets of debts go into the same GDS and TDS calculation a lender would run, because everyone on the mortgage is fully responsible for the whole payment.
Does this account for CMHC mortgage default insurance premiums?
No. If your down payment is under 20%, an insurance premium is added to your mortgage principal and increases your actual monthly payment slightly beyond what this calculator shows. The GDS and TDS limits themselves do not change, but build in a small buffer if your down payment is in that range.
Sources: OSFI Guideline B-20 and Financial Consumer Agency of Canada, mortgage qualification. Reviewed September 29, 2026. This tool estimates a qualifying range and is not a lender's pre-approval.
Take useful notes at your next viewing
A printable worksheet for recording observations, questions and next steps at a home viewing.