Join Date: Jan 2019
Location: Central North Carolina
I would go with 1/3 to 1/2 the board thickness for dowels. Mortise and tenon work, of which dowels are similar, tends to be 1/3 the thickness of the board for the mortise and tenon work. Dowels fall into the same category, but it's really up to the builder to choose the best size for the project.