How much plywood for a 23 square roof?

When talking roofing materials. A square is considered a 10'x10' area or a 100 square feet. So you have 1,900 square feet. There are two basic types of felt: 15lb and 30lb felt. 15lb felt covers 4 sq= Total needed will be 5 rolls 30lb felt covers 2 sq= Total needed will be 10 rolls (*note, 30lb is more thick and better for your roof.