A Word about Paper Weights and Sizes

The US and the UK use different paper sizes and calculate paper “weight” (which usually indicates thickness) differently. Paper also has a grain. It is similar to the grain in wood, and is caused by the tendency of the individual paper fibers to line up along the length of the manufactured roll rather than across it. All these are factors to consider when choosing stock.

In the UK, the most common sizes of sheet are based on one called “AO,” which covers a total of one square meter and measures 33⅛ x 46¾in (841 x 1189mm). This can be cut in half along the long edge to produce an A1 sheet, which is 33⅛ x 23⅜in (841 x 594mm). This can be cut in half in the same way to produce an A2, which is 16½ x 23⅜in (420 x 594mm), and so on. An A4, the standard letter-sized sheet, measures 8¼in (210mm) wide x 11¾in (297mm) tall.

Sheet thickness is based on the weight of a one-meter square; therefore, an A4 page could be 90gsm (grams per square meter) or 130gsm, which would be correspondingly thicker.

Sometimes paper is made fluffier in order to give it added opacity, as in the case of many paperback books. In this case, its weight might be the same as a similar sheet that has been compressed further, but its thickness would be greater.

Of course, printers usually need to print on something larger than an A4 page in order to end up giving you an A4 page. The extra space allows for registration marks, printer’s marks (blocks of varying tints used to measure ink density), or trim marks. So there are two additional size standards, based on the “A” series, which include a set amount of “trim,” the area into which those things useful to a printer can be placed. The smaller of the two adds “R” to the page-size formula (for instance, an RA4 measures 8¼ x 12in/215 x 305mm), and allows for a very small trim. The larger is the “SR” series (as in SRA4, measuring 8¾ x 125⁄8in/225 x 320mm), which gives the printer a bit more space to allow for more information. The SR series is generally easier for printers to work with, and enables them to produce a higherquality end product.

There are two other standard sheet sizes in the UK, the “B” and “C” series. A BO sheet measures 393⁄8 x 555⁄8in (1000 x 1414 mm), and is halved to produce a B1 of 393⁄8 x 277⁄8in (1000 x 707mm) and so on. A CO sheet is 36⅛ x 51in (917 x 1297mm) and halves to give a C1 of 36⅛ x 25½in (917 x 648mm), etc. Note that when halving the long edge dimension of any of these standard sizes produces an odd half millimeter, it is rounded down to the next full number.

In the US, the situation is rather more complicated. Paper falls into three basic groups: text (also called “book”) papers; cover stocks; and a group combining “bond,” “writing,” and “ledger” paper. Sizes for all these are measured in inches, and weights are calculated in terms of how many pounds (lb) 500 sheets (one “ream”) of the “parent” size stock weigh. For text and book papers, the weight is calculated on a ream of parent sheets measuring 25 x 38in. Cover stocks are based on a parent size of 20 x 26in, writing papers on 17 x 22in, and bond and ledger sheets on 19 x 24in. In addition to those, there is also a range of card stocks—used for postcards, for example—that are not measured in terms of weight but in thickness. A typical postcard might be described as 10-point C1S (“C1S” translates as “coated one side”), meaning not that it is as thick as a 10pt type character but that its thickness is 10⁄1000 in.

The standard letter size in the US is 8½ x 11in. Many other standard sizes are available, based on the parent size. For example, a text sheet might be described as an 80lb stock measuring 19 x 25in. Cover stock, which is of course usually heavier, might be given as 60lb and measure 20 x 26in. In both these instances, the second dimension also indicates the grain direction. Therefore a 19 x 25in sheet cannot actually be cut from one measuring 25 x 38in, but it could be cut from one measuring 38 x 25in.

Envelopes can be a real pain. Although there are many different standard sizes, the likelihood of finding the size you want in the stock you want can be slim. If you are designing a job that requires an envelope, think ahead and prepare to be flexible. As you will invariably be asking your printer to order stock for you, it is generally better to check up on envelope availability—and paper, too, if you intend to choose anything that is not fairly run-of-the-mill—and then design the job around stock that you know is available.

To produce your work, the printer will need to purchase sheets of one of the standard sizes. This may be cut down for the press, or used straight out of the package. If you specify an odd page size, it may mean that there is much more “spoilage”—i.e. a higher proportion of the page will have to be cut off and discarded—than if you use something closer to a standard. In such cases, you should not only expect a higher paper cost, you should be aware that you might be asking the printer to work harder than normal. For example, non-standard sizes and orientations can mean a more difficult job for the folder; this means more sheets will be damaged, therefore more will need to be ordered. Also, as paper folds more easily with the grain than against it, heavier stocks that also require folding will either be ordered so that the grain goes with the fold, or an additional score will be added.