Which rate is swap calculated with?

What rate is used for swap calculation: deposit or main refinancing one?

Good examples are European Union and Switzerland. SNB has a negative deposit rate and EU has it at 0 %, while their refinancing rates are 0 and 0.25 (%), correspondingly.

Thank you.

How is a Swap calculated?
The swap is a commission for transfer the opened positions on the next day. Swaps can be negative and positive, depending on the difference in the interest rates of countries whose currencies are traded.

Example of swap calculation:
Let’s consider a trading transaction for the EURUSD pair. Assume the interest rate in Europe is 4.25%, while in the US it’s 3.5%. You open a SELL position for 1 lot EURUSD and sell 100,000 euro, borrowing them at 4.25% APR, and deposit purchased dollars at 3.5% APR. The rate in Europe is higher than that of the US, so the swap will be negative and the sum of the swap will be charged from your account. In the opposite situation, the swap will be deposited to your account.

The swap also includes a broker commission for transferring your position on the next day.

Thus, the swap is 4.25% - 3.5% + 0.1% = 0.85% (the difference between interest rates + broker commission).

The calculation of the swap for selling EUR:
Swap = (value of the contract * (difference between interest rates + commission broker for transferring your position) / 100) * Current price / number of days in the year.

(100,000 * (-0.75% -0.1%) / 100) * 1.5 / 365 = -3.49 USD.

The calculation of the swap for buying EUR:
Swap = (value of the contract * (differencebetween interest rates - broker commission for transferring your position) / 100) * Current Price / number of days in the year.

(100,000 * (0.75% -0.1%) / 100) * 1.5 / 365 = 2.67 USD.

Source from Roboforex

due to the fact that a swap is normally an over the counter product, you can get anything you desire. You just need to ask your banker to create the product for you.