How is rollover calculated for EUR USD vs USD JPY?

Direct answer

Rollover (also called a swap) is the cost or credit you receive for holding a forex position overnight. In general terms, the rollover between EUR/USD and USD/JPY differs because the interest-rate inputs come from different currency legs (EUR vs USD, or USD vs JPY), and because providers may apply specific pricing and conversion adjustments.

Mechanism and definition

A forex position represents exposure to two currencies at once: a base currency and a quote currency. The overnight rollover is intended to approximate the economic effect of the interest-rate difference between those two currencies, for the period you hold the position.

To explain the idea without relying on live market data, use these stable inputs and assumptions:

Interest-rate inputs (conceptual)

The direction and magnitude of rollover depend on which currency’s interest is higher and how that difference is reflected.
For EUR/USD, the relevant comparison is between EUR and USD.
For USD/JPY, the relevant comparison is between USD and JPY.

Trade size and currency conversion (conceptual) Even if the interest-rate difference is the same in “rate terms,” the swap you see is usually translated into money based on:

your position size (lot size or notional),
whether the swap is quoted per unit of the base or quote currency (providers vary in convention),
and the currency you ultimately use to display P/L.

Provider adjustments (conceptual) Providers often do not simply apply a single clean textbook formula. The posted rollover can incorporate additional adjustments such as internal financing conventions, costs, or rounding rules. That means two providers can show different rollover amounts for the same pair and similar underlying interest assumptions.
Multi-day and triple-swap conventions (conceptual) Many rollover systems include an extra accrual for certain days so that the effective “holding period” aligns with how the underlying market settles (often around the weekend). This is commonly described as triple-swap on a particular day.

Evidence or example (with stated assumptions)

Because no real-time prices or provider-specific swap tables are provided here, the example below stays at a verification-friendly, assumption-based level.

Assume for illustration:

You hold one overnight period for each position.
A provider computes rollover from the interest-rate difference between the two currencies.
The provider’s “swap pricing” then converts the result into a cash amount using the trade’s notional and the pair’s quote conventions.

Now compare the pair legs:

EUR/USD uses the EUR leg versus the USD leg.
USD/JPY uses the USD leg versus the JPY leg.

Even if USD versus EUR and USD versus JPY were to produce the same interest difference magnitude in some hypothetical scenario, the provider’s conversion into cash can still differ because the quote currency differs (USD is the quote currency for EUR/USD, while JPY is the quote currency for USD/JPY). In practice, the interest-rate differences will usually not match, so the rollover direction and size generally differ.

A common additional effect is triple-swap: if you hold across the roll date where extra accrual is applied, the rollover you see will be larger (often described as roughly three times a normal day’s accrual). The exact day and the exact multiplier are provider- and system-dependent, so you can’t infer it reliably from the concept alone.

Limitations and risks (material failure modes)

Provider-specific swap tables can change what “calculation” means Two providers may label the same term “rollover,” but the posted values can reflect different internal financing conventions, rounding, or conversion steps. That limits the usefulness of a purely generic formula for predicting the exact cash amount.
Triple-swap timing may not match your expectations If you assume rollover accrues uniformly every calendar day, you can misread the outcome because multi-day conventions concentrate extra accrual into specific roll dates.
Currency conversion and display currency complicate interpretation Even when the interest-rate logic is clear, the displayed swap can be affected by how the provider converts into your account currency and how it treats lot size.
Market conditions can move the underlying interest environment Rollover is linked to interest-rate inputs and system conventions. Those inputs can shift, so relationships observed historically do not guarantee future results.