width  + gusset = total width

Size= total width x height

For example, if the

Width of bag is 8 inches; gusset is 2 inches; and length is 16 inches;

then we will write the size like this:

   (8+2+2) x 16.

                            Length + its bottom gusset size = total length

Size = width x total length

For example, if the

Width of bag is 16 inches; length is 18 inches; and gusset is 2 inches;

 then we will write the size like this:

   16 x (18+2).

Length of bag + length of flap x  width.

For example

12 x 16 + 2 (16 inch length + 2 inch flap x 12 inch width).