All paper bags are made from a single, continuous roll of paper. A paper bag is basically a tube of paper, with a glued seam at the back or side and bottom.

Most paper bags are made from kraft paper. Kraft paper may be unbleached (brown) or bleached (white) and can be made in a wide variety of strengths or thickness, called "basis weight."

How the paper is cut and folded determines the shape of the bag. Four basic paper bags are used for packages that consumers buy: flat, square, satchel-bottom, and self-opening.

The flat bag is the simplest. It is a tube of paper with one end folded under and pasted down to form the bottom. This type of bag often is used to hold nuts, candy, and potato chips.

The square bag is a flat bag, but adds more paper at the side and tucks the paper to form a side panel, called a gusset. If you thrust your hand inside this bag, the bottom will form a square or rectangle, creating a roomier bag. The square bag is used in packaging all types of food products, textiles, hardware, and candy.

The paper grocery bag and many other types of specialty bags are self-opening style (SOS) bags. These bags have gussets and specially precut bottoms that form a square or rectangle. The bag is designed to pop open with the flip of a wrist and stand open while being filled. The square bag is used in packaging all types of food products, textiles, hardware, and candy.

Some retail bags, called duplex bags, are made from two layers of paper. A multiwall bag is two to six bags, one sitting inside of the other. These bags are exceptionally strong because each layer carries its own share of the weight of the product, so the bags often are used to ship large quantities of heavy materials. Dog food, flour shipped to bakeries, and construction materials are among those products packaged in multi-wall bags.

Width is measured from "front" (face) inside seam to inside seam.
Length is measured from the top edge to the bottom fold.
Opening is in the width dimension.
Gusset (or depth) is measured from "side" inside seam to inside seam.

Bag measurements are usually stated as W x G x L, or W x L (without gusset). The first measurement is face width, second measurement is gusseted dimension and third measurement is length, top to bottom.

A gusset is a fold in the bag that enlarges the size of the bag when opened. It can be made as a side or bottom gusset.

The specifications and strength of the paper are usually described in terms of paper thickness, also know as basis weight. The higher the basis weight of the paper, the stronger the bag will be. The symbol # represents pounds. For example, a 30# paper bag has a 30 lb. basis weight. Bags denoted with a pound value less than 30, would use a 30 basis weight strength paper (the lowest strength paper used for bags). For example a 1/2 lb. regular bag would use a paper with a basis weight of 30.

There are five "standard" basis weights - 30, 35, 40, 50, 60 which denote light, medium, and heavy-duty capabilities.

"High-bulk paper" is a paper made thicker than its standard basis weight.

Although Canada uses metric measurement, paper product suppliers usually report their product measurements in nonmetric traditional paper sizes.

Notice in the chart below, bag numbers 6 and 8 have the same stock number and size, but have a different pound and basis weight - the bottom two examples would use a heavier weight paper.