What this page sets up
The calculator opens with Canadian lending rules and Canadian dollars: an 800,000 home with 450,000 owed on the mortgage and 100,000 drawn on the line, at Canadian prime plus 0.5. The borrowing power applies both limits from OSFI’s Guideline B-20, which federally regulated banks follow: the revolving line of credit at no more than 65% of the home’s value, and the line plus the mortgage at no more than 80%. The result shows which one binds.
Interest-only for as long as you like
Canadian HELOCs usually have no fixed draw period: the minimum payment is the interest for as long as the line is open. The page sets five years of interest-only payments and then fifteen years to repay, to show what clearing the balance would cost. Change both to match your plan. The payment shock line tells you how much more a month it takes to actually pay the balance down.
Rates and the comparison
The rate is prime plus your margin, so every Bank of Canada rate change moves your payment. Use the scenarios to see a rise of one to three points. The comparison uses a 25-year refinance at an example 4.5%, the usual Canadian amortization; replace it with a quote, and remember that breaking a fixed-rate mortgage early can cost a prepayment penalty that the table doesn’t include.
The most a HELOC can be under Guideline B-20
The smaller of 80% of the value minus the mortgage and 65% of the value, for common home values and mortgage balances. An asterisk marks where the 65% cap is the limit.
| Home value | No mortgage | 25% owed | 50% owed | 70% owed |
|---|---|---|---|---|
| $400,000 | $260,000* | $220,000 | $120,000 | $40,000 |
| $600,000 | $390,000* | $330,000 | $180,000 | $60,000 |
| $800,000 | $520,000* | $440,000 | $240,000 | $80,000 |
| $1,000,000 | $650,000* | $550,000 | $300,000 | $100,000 |
| $1,500,000 | $975,000* | $825,000 | $450,000 | $150,000 |
Sources: OSFI, Guideline B-20, Residential Mortgage Underwriting Practices and Procedures (HELOCs at most 65% loan-to-value); Bank Act, section 418 (uninsured mortgages at most 80%); Bank of Canada, prime rate 4.45% on September 23, 2026. Provincially regulated credit unions set their own limits. For planning, not financial advice.