Pipe size for shop

If natural gas, using schedule 40 metallic pipe with an inlet pressure less than 2.0 psi and a pressure drop of 0.5 w.c., I use the tables in the Uniform Plumbing Code (2009). All you have to know is your total demand (now and future) in BTU's.

If your gas provider will supply gas at a higher pressure, your pipe size can be reduced, but you will have to install regulators at your appliances.

If propane, that's a different table and the pipe size will be smaller.