Basis weight
Basis weight is the standard measure of paper weight in the U.S., expressed in pounds per 3,000 square feet of a grade's parent sheet. Elsewhere it is reported as grams per square metre (gsm).
Basis weight is reported per 3,000 square feet rather than per square foot for a historical reason: each paper grade has a traditional 'parent sheet' size, and 500 of those sheets — one ream — total 3,000 square feet for most grades. A '20-lb bond' paper means a ream of 17×22 in. sheets weighs 20 pounds.
Different grades use different parent sheets, which is why a 60-lb offset and a 60-lb cover are not the same physical weight. This is one of the most common sources of confusion for buyers comparing basis weights across grade families without converting first.
The metric equivalent, grams per square metre, sidesteps the parent-sheet problem entirely — gsm is the same unit no matter what grade you are weighing. A rough conversion for bond papers is to multiply basis weight in pounds by about 3.76 to get gsm; 20-lb bond is approximately 75 gsm.
On a manifest or order document, basis weight typically appears next to the grade code and is one of the fields used to verify that what was shipped matches what was ordered. A mismatch between the basis weight on the order and the basis weight on the manifest is a common reconciliation error.
Related terms
- LinerboardLinerboard is the flat, smooth paper layer bonded to either side of a corrugated medium to form a corrugated board. It provides the strength, printability, and outer surface of a cardboard box.
- Kraft paperKraft paper is strong, typically brown paper produced by the kraft pulping process — a chemical method that preserves long cellulose fibres. It is the dominant fibre source for linerboard, shipping sacks, and packaging.
- Grams per square metre (gsm)Grams per square metre is the metric system's unit of paper weight — the mass in grams of one square metre of paper. Unlike basis weight, gsm is the same unit across all grades, making cross-grade comparison straightforward.
- Caliper (paper)Caliper is the measure of a paper or board's thickness, typically expressed in thousandths of an inch (points or 'pt') in North America and in micrometres elsewhere. A 12-point board is 0.012 inches thick.
- ReamA ream is the standard unit count for sheet paper sales: 500 sheets in the modern definition, though historically variable (480 or 516 sheets depending on grade and region).
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