This calculator can be used to size a vertical two phase separator for removal of liquid droplets or a vertical Knock Out Drum or Reflux Drum vessel. This calculator determines the minimum required size of such a separator to handle the given flowrates based on terminal settling velocity of liquid droplets (also reported in results). The minimum requirement of residense time between High / Low liquid levels and High High / Low Low alarm levels arise out of process control and alarm requirements. These levels should depend on the project standards. It should be noted that the vessel size calculated here is the minimum approximation and the recommended size should be bigger than this size, with a margin.