Direct answer
Rollover for a forex position is the change in value caused by interest-rate differences between the two currencies in the pair, applied as a swap to your position when it is rolled forward. For USD/CAD versus AUD/USD, the mechanics are the same: you take the “interest leg” for one currency, subtract the “interest leg” for the other currency, then apply the provider’s convention for converting that net amount into what is credited or debited.
Because providers implement rollover with their own published swap rates and operational conventions, the exact numeric result for USD/CAD or AUD/USD can differ between providers and between trade direction (long vs short). Without a provider’s specific swap-rate rules and your position details, you can usually verify only the general logic, not a precise outcome.
Mechanism and definition
Rollover (swap) is an adjustment applied to a leveraged forex position to reflect the effect of carrying positions overnight. In simplified form:
- A forex trade is treated as two offsetting cash positions in different currencies.
- Each currency has an associated interest rate (often represented by an interbank benchmark in theoretical pricing).
- Overnight, the trader’s exposure earns or pays the differential between those two interest rates.
- The result is converted into a swap credit (may be positive) or a swap charge (may be negative) for the trade’s direction.
How the input changes between USD/CAD and AUD/USD
For any pair, the interest-rate differential depends on which currency is in the base/quote structure and whether you are long or short:
- If you are long the pair, you effectively hold one currency exposure and fund the other.
- If you are short, the sign of the interest differential flips.
So for USD/CAD, the relevant currencies are USD and CAD; for AUD/USD, they are AUD and USD. The differential changes when the interest-rate environment changes in USD, CAD, or AUD, and it also changes sign when the trade direction flips.
Provider adjustments and conversion to your account
In real platforms, you usually do not calculate swap directly from a raw market interest differential. Providers publish swap rates (or swap formulas) that may incorporate:
- Their own handling of financing costs and internal pricing.
- Contract specifications such as how swap is expressed (per lot, per day, per unit).
- Currency conversion to match your account currency.
This is why two brokers can show different rollover amounts for “the same” theoretical differential.
Triple-swap convention on rollover days
Many providers implement a triple-swap amount on certain rollover days to reflect longer weekend accrual (commonly Friday to cover the non-business days). Practically, this means that on those days the provider applies an additional factor (often three times the usual single-day rollover) so that accrued interest for multiple days is represented in a single booking.
Evidence or example (with stated assumptions)
Here is a calculation structure you can use to independently verify the logic, without assuming any specific live numbers.
Assumptions (you must replace these with provider-specific details):
- You have a position of size L lots in USD/CAD.
- The provider publishes a swap rate S_day for that trade direction and instrument, expressed as “account currency per lot per day.”
- You hold the position from one rollover time to the next.
General verification steps:
- Identify whether the overnight rollover you are measuring is a “normal” day or a “triple” day.
- Compute expected rollover using the provider’s own rule:
- Normal day: expected rollover ≈ L × S_day
- Triple-swap day: expected rollover ≈ L × (3 × S_day)
- Compare this to the swap credit/charge shown in your statement for that holding period.
Why this works: it tests the provider’s operational convention (their published swap rate and day multiplier), not the underlying macro interest rates.
To compare USD/CAD versus AUD/USD, repeat the same structure for the other instrument. The only differences should be:
- The provider’s swap rate S_day for USD/CAD versus AUD/USD.
- The currency conversion and sign based on whether you are long or short each pair.
If the platform reports rollover for both instruments, matching the day multiplier and direction should make the provider’s bookkeeping consistent even when the underlying interest differential changes.