The actual weight in pounds of 500 sheets of paper (a ream) is the ream weight. If you place a ream of paper on your bathroom scale, it shows you the ream weight. If you know the actual size of the sheets of paper you are weighing, its basis weight, and its basic size, then you can calculate the ream weight without putting the ream of paper on a scale. That assumes you already know what the terms "basis weight" and "basic size" refer to.

### What Is Basis Weight?

The weight, measured in pounds, of 500 sheets of paper *in that paper's basic sheet size* is its basis weight. Even after the paper is trimmed to a smaller size, it is still categorized by the weight of its basic size sheet. The basis weight is indicated on the packaging of most papers. However, the basic sheet size is not the same for all, which causes confusion when comparing different types of paper and their weights.

### What Is Basic Size?

Different types of papers are assigned different basic sheet sizes:

- Bond, copy paper, ledger paper, and rag paper all have a basic sheet size of 17 x 22 inches.
- Offset, book, text, and coated papers have a basic sheet size of 25 x 38 inches.
- Cover stock has a basic sheet size of 20 x 26 inches.
- Tag stock has a basic sheet size of 24 x 36 inches.
- Index stock has a basic sheet size of 25.5 x 30.5 inches.
- Bristol stock has a basic sheet size of 22.5 x 28.5 inches.

### Calculating Ream Weight

To calculate the ream weight, multiply the actual sheet size by the paper's basis weight and divide the result by the paper's basic size. Use this formula:

actual sheet size X basis weight / basic size

Using this formula, the ream weight of 500 sheets (one ream) of tabloid size 11x17-inch, 24 lb.

book paper with the basic size of 25x38 is:

(11x17) x 24 / 25x38 = about 4.72 pounds

If you pick up a ream of letter-size 8.5x11 printer paper at the office supply store and the packaging says it is 20 lb. paper, that doesn't mean the ream weighs 20 pounds. The weight of 500 sheets of the bond paper at its basic size of 17 x 22 inches is 20 pounds. Using the above formula, that ream of 20 lb. paper (bond paper has a basic size of 17x22) actually weighs 5 pounds, not 20.

(8.5x11) x 20 / 17x22 = 5 pounds