When you keep a position open overnight, you are charged a swap, also known as a “rollover fee.”
A swap is the difference in interest rates between the two currencies in the pair being traded.
It is calculated based on the length of your position.
How To Calculate Swap
For forex, The Swap calculation formula is as follows:
(Pip Value * Swap Rate * Nights) / 10
Example of a Rollover
Trading 1 mini lot or 10,000 GBP/USD (long) units with a USD-denominated account.
$1 for a pip
Rate of swap (long): -3.3154
Swap fee(1* -3.3154 * 1) /10= -$0.33