Determing size of models

I created a 3d model of a hexagon that I exported to XNA and I’m planning on instantiating multiple models; however, I need to find out the size of the model in pixels. How would I go about finding that out? Is it listed in blender? Maybe I need to use an XNA method to calculate it. Thanks

Blender models are 3D, pixels are 2D, your question makes no sense.

You can print out a model to a specific size, it is a bit complicated but check out part 10 of the Precision Modelling Guide. It gives a few pointers on how to do it.