http://www.musketeer.ch/blackpowder/homemade_bp.html

3. Two useful recipes.

Usually black powder is a mixture of saltpeter, sulfur and charcoal. Also a black powder without any sulfur yields good results and produces even less smoke. (For how these ingredients are made, see the previous chapters).
A reasonable recipe is a mix of:

100 parts of saltpeter,
18 parts of char coal, and (Parts given by weight)
16 parts of sulfur

If you want to make a powder without sulfur, then mix

100 parts of saltpeter and
24 parts of char coal