On-Screen Display (Beta) Tab:

Stack Size in BB: This feature will display your stack size in Big Blinds. This feature only works in No Limit games! Please be aware that this feature is currently in beta.

Note that the display will update any time it becomes your turn. The display does not update in between turns and thus the number it displays may not be accurate when it is not your turn. Also note that when you post a blind, the posted blind will be counted as part of your stack.

X Position: Use the X position slider bar to set the horizontal position of the display.
Y Position: Use the Y position slider bar to set the verticle position of the display.
Text Size: Use the Text Size slider bar to set the size of the display.
Color: Use the Color chooser to set the color of the display.
Display for Cash Games or Tournaments. Check the Cash Games checkbox activate the display in Cash Games and check the Tournaments checkbox to activate the display in Tournaments.