Post sizes 90x90 or 100x100mm?

[Headbelt]

How do i acertain what post sizes to use? Im building a deck with a pergola and was going to use 90x90 posts but have been thinking i may need 100x100mm. My posts are going to be about 1500 apart along a 190x45 F7 treated pine bearer, posts will be treated pine also.

[bpj1968]

There is no real difference. 90x90 is usually dressed or rougher headed. 100x100 is usually rough sawn