Not sure regarding calories - you'd have to use a web site to see what they say about that portion of an Avocado (like www.dailyplate.com, or www.calorieking.com, www.sparkpeople.com might also have this)
According to the Zone Block Guide though, 1 Tbsp of Avocado is 1 Fat Block containing 1.5g of Fat.
Here is the link to the guide: http://www.zonediet.com/Portals/0/p...0Guide.pdf
Hope this helps! :-)