What GDS measures
Gross Debt Service divides qualifying monthly housing costs by gross monthly household income. Housing costs generally include the qualifying mortgage payment, property taxes, heating and 50% of condominium fees.
- GDS = monthly housing costs ÷ gross monthly income
- A $3,900 housing cost on $10,000 gross monthly income equals 39%
- Lower property costs can leave more room for the mortgage payment
What TDS adds
Total Debt Service uses the same housing costs and adds recurring debt obligations such as car loans, student loans and required credit-card payments. That is why two households with the same income and down payment can receive very different estimates.
- TDS = housing costs + other monthly debts, divided by gross monthly income
- A $500 car payment directly reduces room under the TDS limit
- Paying off debt may matter more than adding the same amount to a down payment
Why your lender's result may differ
The ratio is only one part of underwriting. Credit history, income stability, property type, loan insurance, documentation and lender-specific policies can change the result. Use the ratios to understand sensitivity, then obtain a formal assessment before making a firm commitment.
Try your own numbers
Canada House Affordability Calculator
Change income, debts, down payment, interest rate and property costs to see the calculation update instantly.
Open calculator →