Free calculator · Rates & Terms
Fixed vs Variable Mortgage Calculator
Compare a fixed and a variable mortgage rate side by side to see how rate changes affect your payment and total interest.
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| Measure | Fixed | Variable |
|---|---|---|
| Total interest | — | — |
Estimates only. Results are not a quote, pre-approval, or approval.
How this is calculated
The two paths use different interest conventions, which is deliberate. The fixed path uses Canadian fixed-rate math: the annual rate compounds semi-annually, so the effective monthly rate is (1 + annual rate ÷ 2)1/6 − 1, and the payment is L × i ÷ (1 − (1 + i)−n) for the full amortization. The variable path uses simple monthly interest, annual rate ÷ 12, because variable-rate mortgages are tied to prime and charged on the outstanding balance rather than compounded semi-annually. That difference alone can move the comparison.
Your rate-change scenario is applied to the variable path after the chosen year. When the change takes effect, the tool recomputes the payment over the months that remain, using the new rate and the balance at that point, then continues the schedule. This is how many variable-rate mortgages behave at renewal of the payment, though some lenders hold the payment steady and let the amortization stretch instead.
Read the result with these caveats in mind:
- The variable path is a scenario, not a forecast. Your actual prime rate will move with the Bank of Canada, and this tool only applies the one change you enter.
- A fixed rate buys certainty: the payment and total interest cannot change during the term, while the variable path can rise or fall repeatedly.
- The comparison ignores term renewals, prepayment limits, conversion fees, and any difference in prepayment privileges between the two products.
All figures are estimates for planning only, not a quote, pre-approval, or approval. Confirm current fixed and variable rates, and the terms attached to each, with your lender.