How Rollover Is Calculated for GBP/CAD

Direct answer

Rollover for a GBP/CAD position is typically calculated by applying an interest-related swap value to the trade’s notional amount, then adjusting it using the provider’s own swap-rate convention and timing rules. The key ingredients are (1) the interest-rate differential between GBP and CAD, (2) how the provider converts that differential into a tradable swap price (often including costs and markup), and (3) the rollover cut-off schedule that may cause an extra “triple swap” on certain days.

Mechanism and definition

Rollover (also called swap) is the carrying cost or benefit of holding a currency position overnight. If you keep a GBP/CAD position open past the broker’s daily cut-off time, the account is credited or debited based on the swap convention for that pair and trade direction.

A practical way to explain the calculation is to separate stable mechanics from variable conditions:

Interest-rate differential (stable concept) At a high level, the swap is linked to the difference between the relevant GBP interest rate side and the CAD interest rate side. In simplified terms, if the currency you are “long” tends to have a higher short-term interest component than the currency you are “short,” the position is more likely to receive rollover; the opposite is more likely to produce a cost.
Provider conversion into “swap points” (variable provider condition) Brokers and platforms do not usually post the raw interbank differential as a user-facing figure. Instead, they publish a swap/rollover rate (often in “points” or as a daily percentage of notional) for each pair, direction (buy vs sell), and sometimes contract size rules.
Notional and direction (stable mechanics) Rollover is applied to the trade’s notional amount (the effective exposure size). The sign depends on trade direction: a buy position in GBP/CAD is not the same as a sell position, because the “long” and “short” legs swap against different interest sides.
Timing and special days (convention) Rollover is posted according to the provider’s cut-off. Because markets close over weekends, many providers use a convention where the rollover posted on a specific day reflects multiple days of carry. This is commonly referred to as a “triple swap” period, though the exact days and the way it is implemented depend on the provider’s system.

Evidence or example (with explicit assumptions)

Because different providers publish different swap tables, the most independently verifiable method is to start from your account’s displayed swap/rollover rates.

Assume a simplified setup to make the logic clear (not tied to any one provider):

You hold a GBP/CAD trade overnight and it incurs daily swap.
Your platform provides a daily swap value for the exact instrument and exact direction of your trade.
Your trade has a notional exposure of N in account currency terms (or an equivalent conversion is provided by the platform).

Then the calculation process is conceptually:

Determine the correct daily swap rate from your provider’s table (for GBP/CAD, buy vs sell).
Convert the swap rate into a monetary amount using the trade’s notional/contract-size rules.
Apply special timing: if the overnight crosses into a day with a weekend carry convention, multiply by the appropriate factor (for example, a “triple” rather than a “single” daily post), according to the provider’s rules.

Example arithmetic structure (illustrative):

If the provider’s daily swap amount is S per day for your direction and notional, then a normal rollover event adds S.
If a “triple swap” convention applies at that cut-off, the posted amount would follow 3 × S for that event.

What matters is that you do not rely on generalized interest-rate math alone. Providers can differ in the conversion from interest differential to published swap, and in the timing factor they apply.

Limitations and risks (what can fail)

Provider pricing can diverge from textbook interest differential Even though rollover is linked to interest-rate differentials, the published swap/rollover depends on the provider’s swap-rate model, pricing inputs, and operational rounding. So you may not reproduce the provider’s exact figure using only a generic interest-rate formula.
The “triple swap” depends on cut-off rules The weekend carry convention is not universal in timing.