The Multi-Borrower Pre-Approval Calculator is designed to provide an accurate, lender-aligned estimate of mortgage qualification for individuals or groups of up to four borrowers.
Unlike basic affordability tools, this calculator reflects how lenders in Canada actually evaluate applications by incorporating:
- Income treatment rules
- Debt servicing calculations
- Mortgage default insurance
- Credit and loan-to-value analysis
- Lender classification (Prime, Alternative, Private)
The result is a realistic, strategy-focused pre-approval assessment.
Using the Multi-Borrower Pre-Approval Calculator
Step 1: Enter Borrower Information
Use up to four borrower tabs to input:
- Name
- Residency status (Citizen / PR)
- Occupancy (owner-occupied or non-occupant)
- Credit score
- First-time buyer status (if applicable)
Step 2: Input Income Sources
Add all relevant income types, such as:
- Salary or hourly income
- Bonus or commission
- Self-employment income
- Pension or support income
- Rental income
Each income type is automatically adjusted based on lender guidelines (e.g., averaging, caps, or exclusions).
Step 3: Add Rental Properties (If Applicable)
Select the rental calculation method:
- 50% Offset
- 80% Inclusion
- Net Rental
This affects both qualifying income and debt servicing.
Step 4: Enter Debts
Include all liabilities:
- Mortgages
- Lines of credit
- Credit cards
- Car loans
- Student loans
The calculator applies lender-standard formulas (e.g., 3% of balance for revolving debt).
Step 5: Enter Down Payment
Input all sources:
- Savings
- Gifts
- Investments
- Borrowed funds
The calculator evaluates total down payment and flags potential issues.
Step 6: Review the Summary Tab
The Summary tab consolidates all data and displays:
- Total qualifying income
- Total debt obligations
- GDS and TDS ratios
- Maximum affordability
- Lender fit classification
- Recommendations
Scenario Walkthrough Example: Move Up Buyers
Scenario: Move-Up Buyers with Existing Debt
Two borrowers purchasing a new home:
Borrower 1
- Income: $110,000 (salary)
- Credit Score: 710
- Existing mortgage: $1,800/month
Borrower 2
- Income: $70,000 (salary + bonus averaged)
- Credit Score: 675
- Car loan: $500/month
- Credit card: $8,000 balance
Purchase Details
- Purchase price: $850,000
- Down payment: $120,000 (≈14%)
- Mortgage before insurance: $730,000
Step-by-Step Output Explanation
1. Income Calculation
- Borrower 1: $110,000 (fully usable)
- Borrower 2: $70,000 (adjusted for bonus averaging)
Total qualifying income: ≈ $180,000
2. Debt Calculation
- Mortgage: $1,800
- Car loan: $500
- Credit card: 3% of $8,000 = $240
Total monthly debt: $2,540
3. Mortgage Default Insurance
Because down payment is under 20%:
- Premium ≈ 3.10%
- Premium added to mortgage
Adjusted mortgage: ≈ $752,000
4. Payment Estimate
Assuming:
- Stress-tested rate: ~7%
- Amortization: 25 years
Estimated payment: ≈ $5,300/month
5. Total Obligations
- Mortgage: $5,300
- Existing debts: $2,540
Total: ≈ $7,840/month
6. Ratio Results
- GDS: ~35–37%
- TDS: ~42–44%
Interpretation:
- GDS is within acceptable range
- TDS is near the upper limit
Lender Fit Result
Light Alternative (borderline Prime)
Why:
- Credit score of 675 weakens the file slightly
- Ratios are near limits
- High loan-to-value (insured mortgage)
Key Insights
Strengths
- Strong combined income
- Acceptable GDS ratio
- Sufficient down payment
Cautions
- Credit score below ideal prime threshold
- High TDS ratio
- Insurance increases loan size
Recommendations
The calculator would suggest:
- Reduce revolving debt (credit cards)
- Improve credit score above 680
- Consider increasing down payment slightly
- Review purchase price relative to capacity
What This Means
The borrowers can proceed with the purchase, but:
- They are close to qualification limits
- They may not receive best-in-market rates
- Small improvements could significantly strengthen the file
Technical Specifications
System Design
- Browser-based application (no external data storage)
- Real-time calculation engine using JavaScript
- Multi-borrower architecture (up to four applicants)
Income Engine
- Rule-based income classification
- Supports multiple income types
- Applies lender-specific adjustments:
- 100% inclusion
- Averaging (2-year declining)
- Caps and exclusions
Debt Servicing Engine
Each liability is processed using standardized rules:
- Credit cards → % of balance
- Installment loans → actual or proxy
- HELOCs → interest-only calculation
Reflects actual lender TDS methodology.
Mortgage Calculation Engine
- Uses Canadian mortgage math
- Semi-annual compounding converted to monthly rate
- Supports forward and reverse calculations (payment ↔ mortgage)
Insurance Module
Implements mortgage default insurance rules:
- Down payment thresholds
- Premium tiers
- Purchase price caps
- Amortization restrictions
Premium is capitalized into mortgage.
Ratio Framework
Calculates:
- GDS (Gross Debt Service)
- TDS (Total Debt Service)
Default thresholds:
- GDS: ~39%
- TDS: ~44%
Adjustable within the tool.
Lender Classification Logic
Determines lender fit based on:
- Ratios
- Credit score
- Loan-to-value
Outputs:
- Prime
- Light Alternative
- Heavy Alternative
- Private
The most restrictive factor determines classification.
Recommendation Engine
Generates:
- Strengths
- Cautions
- Next steps
Based on calculated risk factors and thresholds.
Important Notes
- This calculator provides an estimate, not a formal approval
- Results depend on accurate data input
- Lender policies and exceptions may vary
- Property-specific factors are not included
Final Perspective
This calculator is designed to replicate how lenders evaluate mortgage applications in Canada, particularly for more complex, multi-borrower scenarios.
It provides not just an answer, but insight—helping users understand:
- What they qualify for
- Why they qualify
- How to improve their position
