Debt-to-Income Ratio Calculator
Canadian mortgage lenders use two key debt ratios to assess your borrowing capacity: GDS (Gross Debt Service) and TDS (Total Debt Service). Understanding these ratios helps you know how much house you can afford and how existing debts affect your purchasing power before you apply.
Your debt-to-income ratio is calculated on gross monthly income (before tax) and uses stress-tested mortgage payments — not your actual expected payment. This means the amount you qualify for is lower than what you might expect from the posted rate alone.
GDS Ratio (Gross Debt Service)
GDS = (Housing Costs ÷ Gross Monthly Income) × 100
Housing costs include:
- Mortgage payment (at stress-tested rate)
- Property taxes (annual ÷ 12)
- Heating costs (estimated monthly)
- 50% of condo fees (if applicable)
Maximum GDS: 39% (most lenders for insured mortgages)
GDS Calculation Example
| Component | Monthly Amount |
|---|---|
| Mortgage payment (stress-tested) | $2,500 |
| Property taxes | $400 |
| Heating | $150 |
| Condo fees (50%) | $250 |
| Total housing costs | $3,300 |
| Gross monthly income | $10,000 |
| GDS Ratio | 33% ✓ |
TDS Ratio (Total Debt Service)
TDS = (Housing Costs + All Other Debt Payments) ÷ Gross Income × 100
Other debts include:
- Car loans and leases
- Credit card minimum payments (3% of outstanding balance)
- Lines of credit (minimum monthly payment)
- Student loans (OSAP, private)
- Personal loans
- Child support or alimony obligations
Maximum TDS: 44% (most lenders for insured mortgages)
TDS Calculation Example
| Component | Monthly Amount |
|---|---|
| Housing costs (from GDS) | $3,300 |
| Car payment | $450 |
| Credit card minimums (3% of $5,000) | $150 |
| Student loan payment | $200 |
| Total debt payments | $4,100 |
| Gross monthly income | $10,000 |
| TDS Ratio | 41% ✓ |
Credit Cards in TDS Calculations
Canadian lenders include credit card debt in TDS even if you pay your full balance monthly. The standard formula is 3% of the credit card’s outstanding balance (or limit, at some lenders) as a monthly payment obligation.
| Credit Card Balance | Monthly TDS Obligation |
|---|---|
| $5,000 | $150 |
| $10,000 | $300 |
| $20,000 | $600 |
| $30,000 | $900 |
This means a $20,000 credit card balance adds $600/month to your TDS — enough to materially reduce your qualifying mortgage amount. Paying down credit cards before applying can significantly improve your ratios.
Mortgage Debt Ratio Limits by Lender Type
| Lender Type | Max GDS | Max TDS | Notes |
|---|---|---|---|
| Big 5 Banks (insured) | 39% | 44% | CMHC guidelines |
| Big 5 Banks (uninsured) | 39% | 44% | Same; internal policy |
| Credit Unions | 39–42% | 44–47% | Varies by institution |
| B Lenders | 42–50% | 50%+ | Higher rates apply |
| Private Lenders | Flexible | Flexible | Asset-based; very high rates |
Monthly Income Needed by Mortgage Amount
Assuming property taxes $400/month, heating $150/month, no other debts, stress test at 7.0%:
| Mortgage | Monthly Payment* | Min. Gross Income Needed |
|---|---|---|
| $300,000 | $1,800 | $6,100/month |
| $400,000 | $2,400 | $7,600/month |
| $500,000 | $3,000 | $9,100/month |
| $600,000 | $3,600 | $10,600/month |
| $700,000 | $4,200 | $12,200/month |
| $800,000 | $4,800 | $13,700/month |
*Based on 25-year amortization at the 7.0% stress test rate
Self-Employed Applicants
Self-employed borrowers often face a stricter income assessment. Lenders typically calculate qualifying income using:
- 2-year average of net income (Line 15000 on T1 return), or
- Gross-up: Some lenders use net income × 1.15 or 1.25 to account for deductions that don’t represent real expenses (depreciation, home office)
- Stated income programs: Available through B lenders — qualifying at a higher rate
A self-employed person claiming $50,000 in net income but earning $90,000 gross may only qualify based on the $50,000 figure, significantly limiting their GDS/TDS headroom.
How the Stress Test Affects Your Ratios
Canadian mortgage rules require qualifying at the higher of:
- Your contract rate + 2%, or
- The 5-year Bank of Canada benchmark rate (~5.25%)
| Actual Contract Rate | Stress Test Rate | Payment (on $500K, 25yr) | vs Actual |
|---|---|---|---|
| 4.5% | 6.5% | $3,360/month | +$400 vs actual |
| 5.0% | 7.0% | $3,485/month | +$550 vs actual |
| 5.5% | 7.5% | $3,620/month | +$530 vs actual |
Your GDS and TDS ratios are calculated on the stress-tested payment, not the payment you will actually make. This is by design — it ensures you can handle rate increases at renewal.
How to Improve Your Debt Ratios
Lower your GDS
- Buy a less expensive home
- Make a larger down payment to reduce the mortgage amount
- Choose a longer amortization (30 years reduces payment by ~12% vs 25 years)
- Shop in municipalities with lower property taxes
Lower your TDS
- Pay off car loans and personal loans before applying
- Pay down credit card balances (every $10,000 paid off frees ~$300/month in TDS)
- Consolidate multiple debts into a lower single payment
- Increase your gross income through promotion, overtime, or a co-borrower
Increase qualifying income
- Add a co-borrower or guarantor whose income is included
- Document all income sources (rental income, self-employment, side income)
- Wait for a pay increase or new employment before applying
For more on qualifying for a mortgage in Canada, see our mortgage affordability calculator and income needed to afford a home guides.