The book pocket empires has one set of the calculations required. I know there were spreadsheets for this but don't have links handy. 

 

Second option: add the numbers from the Port column for the LoS worlds to get the capacity of the ports to build or repair ships. Then add the numbers from the GWP, which gives a economy to support them. Pick a number between 0.005 and 0.015 to get the annual military budget.