Your debt-to-income (DTI) ratio compares your monthly debt payments to your gross monthly income. It’s the primary metric lenders use when deciding whether to approve a loan and at what rate. A DTI of 36% means 36 cents of every gross dollar you earn goes toward debt payments before taxes. The lower your ratio, the more borrowing room you have and the better your rate.
Canada adds a layer of complexity that most borrowers don’t know about: mortgage lenders use two specific DTI variants — the Gross Debt Service (GDS) ratio and the Total Debt Service (TDS) ratio — defined by CMHC and embedded in the federal mortgage stress test. Understanding both tells you exactly where you stand before you apply for anything.
Two Ratios Lenders Use for Mortgages
| Ratio | What It Includes | Maximum (CMHC Insured) |
|---|---|---|
| Gross Debt Service (GDS) | Mortgage principal + interest + property taxes + heat + 50% of condo fees | 39% |
| Total Debt Service (TDS) | All GDS costs + car loans + student loans + credit card minimums + all other debt | 44% |
GDS measures housing costs only. TDS adds every other debt obligation. Both are calculated as a percentage of gross monthly income — before tax. CMHC-insured mortgages (less than 20% down payment) must satisfy both thresholds. Conventional mortgages are less rigid, but most lenders use the same numbers as a guideline.
How to Calculate Your DTI
Step 1: Add all monthly debt payments
| Debt | Monthly Payment |
|---|---|
| Mortgage (proposed or existing) | $2,100 |
| Car loan | $450 |
| Student loan | $300 |
| Credit card minimums | $150 |
| Line of credit minimum | $100 |
| Total debt payments | $3,100 |
Step 2: Identify gross monthly income
$7,500/month ($90,000 per year ÷ 12)
Step 3: Calculate
$$\text{DTI} = \frac{$3,100}{$7,500} = 41.3%$$
This borrower is under the 44% TDS threshold and would likely qualify for a mortgage — but they are close to the limit. Any additional debt (a new car loan, a personal loan) would push them over.
What Lenders Look For
| DTI Ratio | Lender Assessment |
|---|---|
| Below 36% | Excellent — most products available at best rates |
| 36–40% | Good — will qualify; rates may be slightly higher |
| 40–44% | Acceptable for mortgages; personal loan approval becomes harder |
| 44–50% | High risk — mortgage approval unlikely; alternative lenders only |
| Above 50% | Very high — limited to private lenders at premium rates |
For personal loans and lines of credit outside of mortgages, banks typically want your overall DTI below 40%. Online and alternative lenders may approve up to 50–55%, but at significantly higher interest rates.
The Mortgage Stress Test and Your DTI
Under Canada’s B-20 mortgage rules, lenders must qualify you at the higher of your contract rate plus 2%, or 5.25%. If you’re being offered a 5-year fixed rate of 4.5%, the stress test runs your TDS calculation at 6.5%. This means a borrower who calculates their own TDS as 38% at their actual rate may hit 44%+ under the stress test — and fail.
Before applying for a mortgage:
- Use a mortgage affordability calculator to estimate how much your income actually supports
- Pay down revolving debt (credit cards and lines of credit) — they have minimum payments that inflate TDS
- Avoid financing a vehicle or taking on any new debt in the months before applying
Why DTI Matters Beyond Mortgages
| Loan Type | How DTI Affects It |
|---|---|
| Mortgage | Directly governs approval under B-20 (GDS ≤39%, TDS ≤44%) |
| Personal loan | Most banks want overall DTI below 40% |
| Car loan | High DTI leads to higher rates or outright rejection |
| Line of credit | Banks reduce available credit limit based on total debt load |
| Refinancing | Lower DTI unlocks better refinance rates |
Even if you’re not applying for a mortgage, carrying a high DTI ratio limits what you can borrow and at what price. Lenders see a high DTI as evidence that your income is already stretched — making you a higher default risk.
How to Lower Your DTI
Pay Down the Right Debts First
Not all debt reduction is equal for DTI purposes. Paying off a balance that carries a monthly minimum payment reduces your DTI immediately; paying down a loan that’s almost finished has less impact than eliminating the payment entirely.
| Strategy | DTI Impact |
|---|---|
| Pay off a credit card completely | Eliminates the minimum payment from TDS calculation |
| Pay down a car loan to pay it off early | Removes the payment entirely |
| Consolidate several debts into one lower-payment loan | Can reduce total monthly obligations |
| Avoid new debt before applying | Each new loan immediately raises TDS |
Add Income to the Calculation
| Strategy | Notes |
|---|---|
| Add a co-borrower | Their income is included; their debts also count |
| Document rental income | Lenders count 50–80% of confirmed rental income |
| Document side income | Must be consistent and verifiable (T4s, Notice of Assessment, 2-year history for self-employed) |
A $10,000 increase in gross annual income ($833/month) on the example above drops the DTI from 41.3% to 38.2% — moving from the borderline zone to a comfortable qualification.
DTI and Debt Management
If your DTI is already high and you’re struggling with payments, your ratio is telling you something important: your debt load is consuming too much of your income. The debt payoff strategies that help most in this situation are ones that reduce your monthly obligation — consolidation loans, debt management plans, or in serious cases, a consumer proposal. Each of those tools has a different credit impact, so understanding your options before you act matters.
For a full picture of what you can afford and how to improve your borrowing position, reviewing what to know before taking out a loan and how loan interest is calculated will help you make the right call.