Need advice on sizing posts

[Two shed]

Want to build shed single slope roof.   16ish'.  X 20ish'. .   What size all my  lumber if....
4  posts On two 16' sides.        (front 9' high) . 16' back( 12' high).   Two posts centered for doorway .   Rafters longer than 12'--  overhang. Plywood & shingle roof.  No snow.  Winds rare 60mph .   Thanks .  Also if you know resources where I can go to show me how to calculate in future !

[Two shed]

I meant rafters longer than 20' . I see now I'll need support for rafters midway of 20' length. 2 more posts & a 16' beam ?

[beenthere]

Welcome to the Forestry Forum.

Some sketch of your plan would help. You can also edit your original post with corrections by clicking the "modify" button when at that post.

Also, click on your forum name, and you will see where you can add your location to your profile along with other things. Helps when answering your questions... as to country, where within a country, etc. tks

[S.Hyland]

You wouldn't be related to Arthur "Two Sheds" Jackson would you? ;D

[Magicman]

Welcome to the Forestry Forum, Two shed.  Yup, adding your location to your profile helps.