Guides
Bank of Canada Rate Moves: Variable Mortgage Math
Bank of Canada rate variable mortgage math after the September hold: what a quarter-point move does to a CAD 400,000 payment, and the spread you can cut.
What to take away
- A variable-rate mortgage in Canada is priced off the lender's prime rate, and prime moves when the Bank of Canada changes its overnight rate target.
- On a CAD 400,000 variable mortgage at 4.35 per cent, a 0.25 percentage point cut saves roughly CAD 55 a month at the start; a 0.25 point hike costs about the same.
- The limit in this piece is one borrower, one CAD 400,000 mortgage, no rate forecast and no spare cash to prepay.
- Under that limit, switching to fixed is ruled out, and shopping lenders for a lower spread is the only lever that still works.
- The workaround stops paying once the spread saving falls below about CAD 15 a month.
What the constraint removes
Assume one borrower with a CAD 400,000 variable-rate mortgage amortised over 25 years, a closed term, and no lump-sum prepayment room. No rate forecast is allowed, because nobody has one that holds. No second property, no co-signer, no refinance.
That removes most of the standard advice. You cannot shorten the amortisation. You cannot blend and extend into a better structure. You cannot wait out a cycle on a fixed rate you locked earlier, because the mortgage is already variable.
It also removes the option of doing nothing at all. A variable rate resets with prime whether you watch it or not.
What still works
Payment changes flow through prime. When the Bank of Canada moves its target, Canadian lenders typically adjust prime within days, and a variable mortgage payment or its interest share follows. The latest decision shows the other case: on September 2, 2026, the Bank of Canada held its overnight rate target at 2.25%, so prime, and with it a variable payment, had no reason to move.
The next scheduled announcement is October 28, 2026; the math below shows what a quarter-point move in either direction at that date would do to the payment.
Three levers survive the constraint.
- Call the lender and ask for the current spread, then ask what new customers are being offered on the same product.
- Compare that spread against at least two other lenders, using the same amortisation and term.
- Ask whether the payment is fixed or adjusts with prime, because the two behave differently when rates move.
The spread is the part you can actually change. Prime is not.
Example: one quarter point on CAD 400,000
Start from the prime rate the big banks actually post. In the Bank of Canada's weekly table of interest rates posted by the major chartered banks, the typical prime rate was 4.45 per cent in every reading from September 2 to September 30, 2026, after the hold. Each institution sets its own prime, so check yours.
Take a variable mortgage at prime minus 0.10, which on that prime gives a contract rate of 4.35 per cent. The payments below are illustrative, calculated on a CAD 400,000 balance over a 25-year amortisation with semi-annual compounding, not quoted from a lender. A cut or hike in prime moves the contract rate by the same amount, and the spread stays where it is.
Quarter-Point Move on CAD 400,000
Before move
- Rate
- 4.35%
- Monthly payment
- CAD 2,180
- Change
- —
After cut
- Rate
- 4.10%
- Monthly payment
- CAD 2,125
- Change
- down CAD 55
After hike
- Rate
- 4.60%
- Monthly payment
- CAD 2,235
- Change
- up CAD 55
One quarter point on CAD 400,000
Rate
- Before a 0.25 point cut
- 4.35%
- After a 0.25 point cut
- 4.10%
- Before a 0.25 point hike
- 4.35%
- After a 0.25 point hike
- 4.60%
Monthly payment
- Before a 0.25 point cut
- about CAD 2,180
- After a 0.25 point cut
- about CAD 2,125
- Before a 0.25 point hike
- about CAD 2,180
- After a 0.25 point hike
- about CAD 2,235
Change
- Before a 0.25 point cut
- After a 0.25 point cut
- down CAD 55
- Before a 0.25 point hike
- After a 0.25 point hike
- up CAD 55
The same arithmetic runs in reverse on the way up. A full percentage point of hikes adds roughly CAD 220 a month at this balance. That is the number to hold in your head, not the headline rate.
The Bank of Canada publishes each decision as a scheduled policy interest rate announcement, and its Monetary Policy Report sets out the reasoning. The Bank of Canada's overview of the overnight rate target explains how that target feeds into prime.
Compromises worth making
Switching lenders inside the same term usually means paying a penalty, so the honest move is to negotiate the spread at renewal. That costs a phone call and nothing else.
Renewal Negotiation Checklist
- Confirm current contract rate and spread over prime
- Ask what new customers get on the same product
- Get two written comparisons at the same amortisation
- Ask whether payment adjusts with prime or stays fixed
If the mortgage is up for renewal within a year, asking for a shorter term is reasonable. It keeps the variable exposure but buys a fresh negotiation sooner.
A small increase to the payment, if the lender allows it without penalty, cuts total interest. Under this constraint there is no spare cash, so treat that as a last resort.
- Confirm current contract rate and spread over prime
- Ask what new customers get on the same product
- Get two written comparisons at the same amortisation
- Ask whether the payment adjusts with prime or stays fixed
Compromises that are not
Breaking the term to chase a lower spread rarely pays. Penalties on variable mortgages are often three months of interest, which can exceed a year of the saving.
Stretching the amortisation back to 30 years to lower the payment adds interest over the life of the loan and does not reduce the rate.
Taking a fixed rate purely because it feels safer is a rate forecast by another name. Under this constraint, no forecast is allowed, so that choice has to be argued on cash-flow certainty alone.
A lower spread is a saving you can measure today. A rate forecast is a guess you cannot.
When to stop and resource it properly
The workaround stops paying when the best spread you can negotiate saves less than about CAD 15 a month. At that point the phone calls and comparisons cost more in time than they return.
It also stops paying if a penalty quote comes back above roughly CAD 500, because the break-even stretches past the term.
When either threshold is hit, stop shopping and put the effort into a mortgage broker or a fee-only planner instead. That is the point where a professional opinion is worth paying for.
