Making Sense of Paper Weights
Terms describing paper sizes and weights can sound confusing especially when you are new to working with paper or used to a particular format. There are basically two standards in the world, metric (ISO) and one standard in the United States. Paper sizes are related to letter size as this is the most commonly used format. ISO letter size is ‘A4’ size or 210 by 297 millimetres (mm). In the United States letter size is ‘A’ size or 8 1/2 by 11 inches (in or “). Paper sizes are organised into series based on folding a standard large sheet of paper into a smaller letter size or book page size.
Aspect ratio
An aspect ratio is the ratio of one side of a sheet to the other side. A sheet that is 4 by 2 inches has an aspect ratio of 2. A sheet of paper that is 8 by 4 has an aspect ratio of 2 as well. When giving an aspect ratio as two numbers, the horizontal dimension or width is always given first, and the vertical dimension, or height is given second. An aspect ratio greater than 1 is called a landscape aspect ratio because most landscape paintings are wider than they are tall. An aspect ratio less than 1 is called a portrait aspect ratio because most portrait paintings are narrower than they are tall.
Any point on the diagonal gives the same aspect ration irrespective of size.
Under the metric (ISO) standard the aspect ratio is the same for all paper sizes, the only aspect ratio for which this is possible is the square root of two. Using ISO, when an image is enlarged from one paper size to another, the image fits exactly. Under the United States standard, when enlarging page size from ‘A’ Size to ‘B’ Size, the aspect ratio changes. When you enlarge an 8 1/2 x 11 inch image to 11 x 17 inches, it does not fit exactly.
Paper sizes
The basic size of metric paper is one square metre, which is the area of an A0 sheet of paper. This size, taken along with the aspect ratio, determines the size and shape of metric reprographics paper.
For a given sheet size, United States paper is a little wider than metric paper in the short dimension, and a little shorter than metric paper in the long dimension.
As can be seen on the chart below, A0 size folded once is A1 size, folded twice is A2 size, folded thrice is A3 size, and folded 4 times is A4 size. Metric paper also has a B series of sizes for posters and wallcharts. There is also a C series of sizes for envelopes.
Metric and US trimmed paper sizes
| Metric Name | Metric Size in mm | Size in Inches | US Size | Size in Inches |
|---|---|---|---|---|
| A8 | 53 x 74 | 2.07 x 2.91 | Business card | 2 x 3 1/2 |
| A7 | 74 x 105 | 2.91 x 4.13 | 3 x 5 | 3 x 5 |
| A6 | 105 x 148 | 4.13 x 5.83 | Microfiche | 4.13 x 5.83 |
| A5 | 148 x 210 | 5.83 x 8.27 | 5 x 8 | 5 x 8 |
| A4 | 210 x 297 | 8.27 x 11.69 | A | 8 1/2 x 11 |
| A3 | 297 x 420 | 11.69 x 16.54 | B | 11 x 17 |
| A2 | 420 x 594 | 16.54 x 23.39 | C | 17 x 22 |
| A1 | 594 x 841 | 23.39 x 33.11 | D | 22 x 34 |
| A0 | 841 x 1189 | 33.11 x 46.81 | E | 34 x 44 |
| 2A | 1189 x 1681 | 46.81 x 66.22 | - | - |
| A Series | Formats | B Series | Formats |
|---|---|---|---|
| 4AO | 1682 x 2378 | - | - |
| 2AO | 1189 x 1682 | - | - |
| AO | 841 x 1189 | BO | 1000 × 1414 |
| A1 | 594 x 841 | B1 | 707 × 1000 |
| A2 | 420 x 594 | B2 | 500 × 707 |
| A3 | 297 x 420 | B3 | 353 x 500 |
| A4 | 210 x 420 | B4 | 250 × 353 |
| A5 | 148 x 210 | B5 | 176 × 250 |
| A6 | 105 x 148 | B6 | 125 × 176 |
| A7 | 74 x 105 | B7 | 88 × 125 |
| A8 | 52 x 74 | B8 | 62 × 88 |
| A9 | 37 x 52 | B9 | 44 × 62 |
| A10 | 26 x 37 | B10 | 31 x 44 |
Popular uses
| A0 | Technical drawings, posters |
| A1 | Technical drawings, posters, flip charts |
| A2 | Flip charts, drawings, diagrams, large tables |
| A3 | Drawings, diagrams, large tables |
| A4 | Letters, magazines, forms, catalogues, laser printer and copying machine output |
| A5 | Note pads |
| A6 | Postcards, books |
| B5, A5, B6 | Books |
| C4, C5, C6 | Envelopes for A4 letters: unfolded (C4), folded once (C5), folded twice (C6) |
| B4, A3 | Newspapers, supported by most copying machines in addition to A4 |
| B8, A8 | Playing cards |
Weights of paper
The weight of metric paper is specified in grams per square metre (gms). One square metre is one A0 size sheet or 16 A4 size sheets. The weight of United States letter size paper is specified in pounds (lbs) per 500 sheet ream of uncut C size (17 x 22 inches) paper. For the letter size paper, a sheet is cut into 4 pages so that a cut ream of letter size paper, 500 letter size sheets, weighs 4 pounds if the paper is nominally 20 pound paper.
Popular weights of paper (Metric/US):
| 80 - 100gsm/20lb | Copier paper, uncoated |
| 100-120gsm/24lb | Letterhead and stationery paper |
| 135-200gsm/70-80lb | Text paper is this is used in books, magazines and annual reports |
| 200-300gsm/60-100lb | Cover stock is the heaviest paper and is typically used for postcards, business cards, paperback book covers, etc. |