Understanding GDS and TDS Ratios

Key metrics lenders use to assess your mortgage affordability

What Are Debt Service Ratios?

Debt service ratios are calculations that lenders use to determine how much mortgage debt you can reasonably afford based on your income. In Canada, there are two primary ratios that lenders evaluate:

  • GDS (Gross Debt Service) Ratio - Housing costs only
  • TDS (Total Debt Service) Ratio - All debt obligations

These ratios help ensure you won't become over-extended financially and can comfortably manage your mortgage payments along with your other financial obligations.

GDS Ratio (Gross Debt Service)

GDS = (Housing Costs ÷ Gross Income) × 100

What's Included in Housing Costs?

  • Monthly mortgage payment (principal and interest)
  • Property taxes (monthly portion)
  • Heating costs
  • 50% of condo fees (if applicable)

GDS Guidelines

Maximum recommended: 32-39%

Most lenders prefer your GDS ratio to be below 32%, though some may allow up to 39% depending on your overall financial profile and credit strength.

GDS Calculation Example

Gross Monthly Income: $6,000

Housing Costs:

  • Mortgage payment: $1,500
  • Property taxes: $250
  • Heating: $100
  • Condo fees (50%): $150
  • Total: $2,000

GDS Ratio: ($2,000 ÷ $6,000) × 100 = 33.3%

TDS Ratio (Total Debt Service)

TDS = (Housing Costs + Other Debts ÷ Gross Income) × 100

What's Included in Total Debts?

  • All housing costs (from GDS calculation)
  • Credit card payments (minimum monthly payment)
  • Car loans or leases
  • Student loans
  • Personal loans or lines of credit
  • Other debt obligations

TDS Guidelines

Maximum recommended: 40-44%

Lenders typically want your TDS ratio below 40%, though some may accept up to 44% for borrowers with strong credit and stable income.

TDS Calculation Example

Gross Monthly Income: $6,000

Total Debt Obligations:

  • Housing costs: $2,000
  • Car loan: $400
  • Credit card minimum: $100
  • Student loan: $200
  • Total: $2,700

TDS Ratio: ($2,700 ÷ $6,000) × 100 = 45%

⚠️ This ratio exceeds recommended guidelines

Why These Ratios Matter

For Lenders

  • Assess your ability to repay the mortgage
  • Determine maximum loan amount
  • Evaluate financial stability
  • Comply with lending regulations

For You

  • Understand your true affordability
  • Avoid over-extending financially
  • Plan for comfortable payments
  • Leave room for savings and emergencies

How to Improve Your Ratios

💰 Increase Your Income

  • Include all sources of income
  • Add a co-borrower
  • Consider bonus/commission income
  • Document rental income

📉 Pay Down Debt

  • Pay off credit cards
  • Eliminate car loans early
  • Consolidate high-interest debt
  • Close unused credit accounts

🏠 Adjust Housing Budget

  • Look at lower-priced homes
  • Make a larger down payment
  • Consider a longer amortization
  • Shop for lower property taxes

⏰ Time Your Purchase

  • Wait until debts are paid off
  • Delay until income increases
  • Build up your down payment
  • Improve your credit score first

Important Considerations

🏦 Different Lenders, Different Rules

While the general guidelines are 32% for GDS and 40% for TDS, different lenders may have varying requirements:

  • Traditional Banks: Usually strict with standard ratios
  • Credit Unions: May offer more flexibility
  • Alternative Lenders: May accept higher ratios but with higher rates
  • Insured vs. Uninsured: Insured mortgages may have stricter requirements

📊 Stress Test Impact

Your ratios are calculated using the stress test rate (the higher of your contract rate + 2% or 5.25%), not your actual mortgage rate. This means you're qualified based on a higher payment than you'll actually make, providing a safety cushion.

💡 Beyond the Numbers

Even if you qualify for a certain amount, consider your lifestyle and financial goals:

  • Do you want room in your budget for vacations and entertainment?
  • Are you planning to have children or other major life changes?
  • Do you have emergency savings beyond your down payment?
  • Are your job and income stable and secure?

Ready to Calculate Your Ratios?

Use our mortgage calculator to see how different scenarios affect your GDS and TDS ratios, or contact us for a personalized assessment.

Affordability Calculator

Last Updated: May 2026

Disclaimer: This guide provides general information about debt service ratios for educational purposes only. Actual lending requirements vary by institution and your individual circumstances. Always consult with a licensed mortgage professional for personalized advice.

Frequently Asked Questions

What is the GDS ratio for a mortgage in Canada? +
The Gross Debt Service (GDS) ratio is the percentage of your gross monthly income needed to cover your housing costs — including your mortgage payment (principal and interest), property taxes, heating costs, and 50% of condo fees if applicable. Canadian lenders require a GDS ratio of 39% or less. Most prefer it below 32% for the strongest approval.
What is the TDS ratio and how is it different from GDS? +
The Total Debt Service (TDS) ratio measures all your monthly debt obligations as a percentage of gross income — your housing costs (same as GDS) plus all other debts such as car loans, credit card minimum payments, student loans, and personal lines of credit. Canadian lenders require a TDS of 44% or less. GDS only looks at housing; TDS looks at everything.
What GDS and TDS ratios do I need to get approved for a mortgage in Canada? +
Most federally regulated lenders in Canada require a GDS ratio of 39% or less and a TDS ratio of 44% or less. These are the maximum limits — lower is better. Many lenders prefer GDS below 32% and TDS below 40% for the best rates and easiest approval. These ratios are calculated using the stress test qualifying rate, not your actual contract rate, which makes them harder to meet.
What happens if my TDS ratio is too high? +
If your TDS ratio exceeds 44%, federally regulated lenders will typically decline your mortgage application. Your options include: paying down existing debts to reduce monthly obligations, adding a co-borrower to increase total income, reducing your target home price, making a larger down payment to reduce the mortgage amount, or exploring alternative lenders (credit unions, private lenders) that may have more flexible requirements but often charge higher rates.
Does the mortgage stress test affect my GDS and TDS ratios? +
Yes, significantly. Your GDS and TDS ratios are calculated using the stress test qualifying rate — the higher of your contract rate plus 2% or 5.25% — not your actual mortgage rate. This means your calculated mortgage payment is higher than what you will actually pay, which makes your ratios look worse than reality. For example, a 4.59% contract rate becomes a 6.59% qualifying rate, increasing your calculated monthly payment by roughly 15–20%.
Can rental income be used to improve my GDS and TDS ratios? +
Yes. If you have rental income from an investment property or a basement suite in the home you are buying, most lenders will include a portion of that rental income in your gross income calculation, which improves your ratios. Typically, lenders will use 50–80% of rental income (to account for vacancies and expenses). You will need to document the rental income with a lease agreement or tax returns.