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Paper and Notebook Sizes Explained

Moleskine Notebook
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Paper and notebook sizes are an unfortunately confusing thing. You just want some printer paper or a new notebook, and instead you are choosing between “A4” and “B5” and a slew of other unhelpful options. Maybe you are better off switching to numbers, like “8.5 by 11,” but we’ve all made the mistake of ordering legal paper when we meant to get normal copy paper.

This guide should help you sort out all your loose leaf paper and notebook size problems.

Paper Size Standards

A4, A6, and so on are not sizes that were arrived a randomly, they are the result of ISO standard 216. ISO 216 defines paper sizes in the “A” and “B” series with ISO 217 and ISO 269 (specifically the “C” series) standards handling related products, like envelopes.

Midori MD Deskpad A4
An A4 desk pad

ISO vs. US

In the United States it’s common to see sizes like A4, but paper is more commonly referred to as “Letter,” “Legal,” “Memo” or terms like that. This is because the US is based on ANSI (American National Standards Institute) standards, which are different from ISO (an international standard). Names like “letter size” are actually not the official names, but rather shorthand for the ANSI name.

The primary paper sizes in the US standard are:

  • Legal: 8 1/2 x 14 inches / 216 x 356 mm
  • Letter (ANSI A): 8 1/2 x 12 2/3 inches / 216 x 322 mm
  • Government Letter: 8 x 10 inches / 203 x 254 mm

The specific standard here is known as ANSI/ASME Y14.1 if you want to do more research. Unfortunately this document isn’t free, so it won’t be accessible or practical for everyone to use.

Paper Size Grid
Courtesy Wikipedia

Understanding Paper Size Naming

The paper and notebook names themselves are quite simple: you have a series name and then a size name. In the ISO standard these combine to make “A4” or “B6”. The challenge here is remembering what those sizes mean and how big they are relative to one another.

The most important rule to remember is that the sizes are in inverse order, so size 0 paper is larger than size 5!

The ISO sizes are related to one another, though it might not immediately be clear how. They use an aspect ratio of √2:1. This allows for a half sheet to have the same aspect ratio of the original, which means a single sheet can be bound and folded in half, preserving the requires width to length ratio.

Importantly, the height-to-width ratio of all pages is √2 (basically a ratio of 1.41:1).

Note how the sizes are reused: an A0 sheet is 841 mm wide and an A1 sheet is 841 mm tall. This means two of a small sizer can be rotated and put side-by-side to great the next size up.

A Series Paper Sizes

The most common paper sizes are part of the “A” format, which contains commonly referred to types of loose paper, like “printer paper” and “legal paper.” These names are often shorthand that are used to refer to standard sizes, but they can also refer to ANSI sizes, so you have to be careful what you ask for!

  • A0: 841 x 1189 mm (33 1/8 x 46 19/24 inches)
  • A1: 594 x 841 mm (23 3/8 x 33 1/8 inches)
  • A2: 420 x 594 mm (16 13/24 x 23 3/8 inches)
  • A3: 297 x 420 mm (11 17/24 x 16 13/24 inches)
  • A4: 210 x 297 mm (8 1/4 x 11 17/24 inches)
  • A5: 148 x 210 mm (5 5/6 x 8 1/4 inches)
  • A6: 105 x 148 mm (4 1/8 x 5 5/6 inches)
  • A7: 74 x 105 mm (2 11/12 x 4 1/8 inches)
  • A8: 52 x 74 mm (2 1/24 x 2 11/12 inches)
  • A9: 37 x 52 mm (1 11/24 x 2 1/24 inches)
  • A10: 26 x 37 mm (1 1/24 x 1 11/24 inches)

A helpful tip is that as you know up in number with the A family, the paper size halves. This means a notebook that is size A5 is about half the size of an A4 sheet!

B Series Paper Sizes

These are paper sizes that are different from A series sizes, but not necessarily smaller or larger. B sizes might just seem like weird sizes, but they can be quite useful if you can get your head around the range.

B sizes are √2 times greater in total area than the equivalent A size.

  • B0: 1000 x 1414 mm (39 3/8 x 55 2/3 inches)
  • B1: 707 x 1000 mm (27 5/6 x 39 3/8 inches)
  • B2: 500 x 707 mm (19 2/3 x 27 5/6 inches)
  • B3: 353 x 500 mm (13 11/12 x 19 2/3 inches)
  • B4: 250 x 353 mm (9 5/6 x 13 11/12 inches)
  • B5: 176 x 250 mm (6 11/12 x 9 5/6 inches)
  • B6: 125 x 176 mm (4 11/12 x 6 11/12 inches)
  • B7: 88 x 125 mm (3 11/24 x 4 11/12 inches)
  • B8: 62 x 88 mm (2 11/24 x 3 11/24 inches)
  • B9: 44 x 62 mm (1 3/4 x 2 11/24 inches)
  • B10: 31 x 44 mm (1 5/24 x 1 3/4 inches)

C Series Paper Sizes

These are the ISO standards for envelopes and other related paper products. They are similar to the A format but slightly larger in size.

  • C0: 917 x 1297 mm / 36 1⁄12 x 51 1⁄12 inches
  • C1: 648 x 917 mm / 25 1⁄2 x 36 1⁄12 inches
  • C2: 458 x 648 mm / 18 1⁄24 x 25 1⁄2 inches
  • C3: 324 x 458 mm / 12 3⁄4 x 18 1⁄24 inches
  • C4: 229 x 324 mm / 9 x 12 3⁄4 inches
  • C5: 162 x 229 mm / 6 3⁄8 x 9 inches
  • C6: 114 x 162 mm / 4 1⁄2 x 6 3⁄8 inches
  • C7: 81 x 114 mm / 3 5⁄24 x 4 1⁄2 inches
  • C8: 57 x 81 mm / 2 1⁄4 x 3 5⁄24 inches
  • C9: 40 x 57 mm / 1 7⁄12 x 2 1⁄4 inches
  • C10: 28 x 40 mm / 1 1⁄12 x 1 7⁄12 inches

Other Paper Sizes

Keep in mind that there are many other paper sizes. First of all, paper doesn’t have to adhere to a standard at all! Paper and notebook makers are free to create products that are any size they want. That said, it can be prohibitively expensive to create paper in custom sizes and it can be difficult to do at scale.

There are also standard sizes that are quite rare. These include huge sizes like 4A0, which is an enormous 1682 x 2378 mm (about 5 by 7 feet), and 2A0 which is 1189 x 1682 mm.

There are other sizes that are variants on the mainline sizes. These come in sizes like “A4 extra” (235 x 322 mm / 9.25 x 12.67 inches) and “A4 Super” (229 x 322 mm / 9.25 x 12.67 inches). So, as you might have suspected, there is an endless array of paper sizes.

Notebooks Sizes

While notebooks appear as custom sizes much more often than loose paper does, many do adhere to the standard sizes mentioned above. For example, almost all Japanese notebooks are sold in standard dimensions, like the Midori A4 desk pad or the Midori A5 notebook. You will typically see journals (like those used for Bullet journaling) in A5 or B5 sizes.

While A sizes are common in the US, you’ll see B sizes much more often in Japan and South Korean. This doesn’t make a major difference to buyers as the A and B sizes overlap with one another, but you might have a preference for, say, a B5 over the slightly larger A4.

This might seem obvious, but it’s worth making clear: notebook sizes are the same as paper sizes. This means an A4 notebook will basically be sheets of A4 paper that are bound together.

Moleskine Notebook Sizes

Not every company feels the need to adhere to standard sizes, Moleskine in particular. Here are handy reference sizes for Moleskine Cahier journals and Classic notebooks:

  • Moleskine Extra Small: 6.5 x 10.5 cm / 2.5 x 4.3 inches
  • Moleskine Pocket: 9 x 14 cm / 3.5 x 5.5 inches
  • Moleskine Large: 13 x 21 cm / 5.1 x 8.4 inches
  • Moleskine Extra Large: 19 x 25 cm / 7.5 x 9.8 inches
  • Moleskine A4: 21 x 30 cm / 8.3 x 11.7 inches

Rhodia Notebook Sizes

The popular Rhodia notebooks also use custom sizing that can be a bit confusing. Here are the company Pad sizes…

  • Pad 8: 7.4 x 21 cm / 3.0 x 8.3 inches
  • Pad 10: 5.2 x 7.5 cm / 2.0 x 3.0 inches
  • Pad 11 (A7): 7.4 x 10.5 cm / 2.9 x 4.1 inches
  • Pad 12: 8.5 x 12 cm / 3.4 x 4.7 inches
  • Pad 13 (A6): 10.5 x 14.8 cm / 4.1 x 5.8 inches
  • Pad 16 (A5): 14.8 x 21 cm / 5.8 x 8.3 inches
  • Pad 18 (A4): 21 x 29.7 cm / 8.3 x 11.7 inches
  • Pad 19 (A4+): 21 x 31.8 cm / 8.3 x 12.5 inches
  • Pad 38 (A3+): 42 x 31.8 cm / 16.5 x 12.5 inches

Once you move the Dot Pad, sidebound notebook, R By Rhodia, or other lines there are additional size specifications.

Frequently Asked Questions

What is a standard printer paper size?

Standard printer paper in the United State and Canada is called “letter” paper as per the ANSI standard. It’s sized at 8.5 x 11 inches. Other parts of the world use A4 as their standard printer paper, which is 210 x 297 mm (8 1⁄4 x 11 17⁄24 inches).

What is a standard envelop size?

Normal North American business envelopes are size #10. They measure 4 1/8 by 9 1/2 inches.