How Rollover Is Calculated for Major vs Minor Currency Pairs

Direct answer

Rollover (often called a swap) is an adjustment added or subtracted when a position is held overnight. For both major and minor pairs, the starting driver is the interest-rate difference between the two currencies, but the final rollover you see is also shaped by the provider’s pricing model and the platform’s rollover convention (including how triple-swap timing is handled).

Mechanism and definitions

Rollover / swap concept: When you hold a currency position beyond the broker’s daily cutoff, the trade is “rolled over” to the next value date. Because holding one currency instead of the other has an interest cost or benefit, rollover represents the net interest effect for the two currencies.

Interest-rate inputs (the core variable): In a simplified view, rollover is related to the difference between the interest rates of the two currencies in the pair. If one currency’s benchmark rate is higher than the other’s, the position may receive a credit or incur a debit depending on whether you are long or short that currency exposure.

Why majors vs minors can differ:

• The interest-rate gap may be different between currency combinations, even if the rollover logic is the same.
• Liquidity and pricing quality often differ: majors tend to trade more actively, while minors can have wider bid/ask spreads and different execution costs. While those costs are not “the rollover math” itself, they can affect the total economics of holding overnight.
• Provider adjustments: the amount you see is not purely a theoretical interest differential. Providers typically quote rollover based on their own net cost of financing, hedging, and pricing adjustments.

Triple-swap convention (timing detail): Many platforms apply a larger rollover on certain days (commonly associated with the weekend period) to cover more than one day of holding. The exact day and multiplier depend on the platform’s rollover convention, but the general idea is that positions that would otherwise span additional non-business time receive an extra adjustment.

Evidence or example (with explicit assumptions)

Because there are no universal, publicly identical swap formulas across providers, the most reliable way to understand rollover for major vs minor pairs is to separate the calculation into conceptual layers and then map them to what your provider displays.

Assumptions for the example

Assume:

1. Rollover is proportional to the interest-rate differential.
2. The provider quotes a “buy” and “sell” rollover for each pair.
3. On a specific rollover day, the provider applies a multiplier (for example, 3×) to account for additional calendar time.

Example structure (not provider-specific numbers)

Let:

• Currency A has higher benchmark interest than Currency B.
• You are long the pair quoted as A/B (meaning you are effectively long A exposure).
• The broker’s convention yields a positive rollover for long positions when A’s rate is higher.

Then a conceptual overnight rollover could be described as:

• Base daily rollover = function(interest-rate differential, pair convention)
• Quoted rollover = base daily rollover × provider pricing factor
• Weekend/extra-day rollover = quoted rollover × time multiplier

For major vs minor pairs, the interest-rate differential component may lead to different base outcomes. Meanwhile, provider pricing factors and weekend multipliers are structural features of how rollover is quoted, not a property of majors or minors by definition.

Limitations and risks / failure modes

1. Different providers publish different rollover numbers: Even if they both use an interest-rate concept, the quoted swap reflects provider-specific pricing, hedging, and costs.
2. Timing matters: Rollover is applied relative to a daily cutoff. If your position is opened/closed near that time, the actual swap you experience may not match a simple expectation.
3. Triple-swap or extra-day rules may differ: Some platforms apply multipliers on different days, and the multiplier magnitude can vary. Assuming a fixed 3× rule without checking your platform’s displayed convention can lead to incorrect expectations.
4. Total overnight cost can be more than swap: Spreads, commissions, and execution effects can change the economics of holding overnight, especially for minors that may have wider pricing.
5. Market conditions change: Interest-rate curves and funding expectations move over time, so historical patterns cannot reliably predict future rollover outcomes.