There are 2 types of margin calculated. Initial margin and Maintenance margin. We calculate the margin amount as the amount of Equity that will be reserved to open or maintain a position. 

Long call/put
Initial margin Reference price (*) of the option
Maintenance Margin same as Initial Margin


Short call
Initial margin

Maximum ((20%  * Underlying Price - Out of the Money Amount), 
(10% * Underlying Price)) 
Maintenance margin 10% * Underlying Price

Short put
Initial margin

Maximum ((20%  * Underlying Price - Out of the Money Amount), 
(10% * Underlying Price)) 
Maintenance margin 10% * Underlying Price

(*) Mark price of an option is the current price of the option as calculated by our risk management system. Usually this is the average between bid and ask, but for risk management purposes there are hard limits to this price. For example currently if the average between bid and ask of a certain option has an implied volatility higher than 100%, the mark price will be 100% implied volatility, and if the average of bid ask has an implied volatility lower than 30%, the mark price will be 30% volatility. Further if there is no market at all in an option (empty order book), the option will be valued at an implied volatility 60%.

The values 30%, 60% and 100% can be changed by risk management without prior notice, depending on market circumstances.