Stated in pounds per ream, it depends on the basic size assigned to each grade family: 17 x 22 inches for bond, 25 x 38 inches for book and offset, 20 x 26 inches for cover. That is why 20 lb bond and 50 lb offset weigh about the same per square meter, near 75 g/m2. Mill people often use basis weight loosely to mean grammage, which confuses metric customers.
It's 50-pound offset in basis weight, which is 74 grams for the guys in the Montreal office.
Ask for grammage whenever a basis weight comes without its grade family; 50 lb means very different sheets in bond, book and cover.
Also heard as
- ream weight
- basis
Related terms
Grammage
Mass of paper per unit area in grams per square meter, the base for most optical calculations.
Caliper
Thickness of a single sheet of paper, measured under a set pressure and given in micrometers or thousandths of an inch.
Bulk
Volume per unit mass of paper, the inverse of density, usually given in cubic centimeters per gram.