Last edited 12 Oct 2020

North American Paper Sizes

The United States, Canada, and in part Mexico, are the only industrialized nations in which the ISO 216 standard paper sizes are not yet widely used. The current standard sizes are unique to that continent (though with globalisation other parts of the world have become increasingly familiar with them).

The traditional North American inch-based sizes "Letter", "Legal", "Ledger", and "Tabloid" are by far the most commonly used of these for everyday activities. Outside of North America, Letter size (8 1⁄2 in × 11 in or 215.9 mm × 279.4 mm) is also known as "American Quarto" and the size is almost exactly one quarter of the old Imperial (British) paper size known as Demy (17½ in ×22½ in or 445 mm × 572 mm), allowing ½ inch for trimming.

There are many other unsystematic formats for various applications in use. The “Letter”, “Legal”, “Tabloid”, and other formats (although not these names) are defined in the American National Standard ANSI X3.151-1987.

While all ISO paper formats have consistently the same aspect ratio of √2 = 1.414, the U.S. format series has two different alternating aspect ratios 17/11 = 1.545 and 22/17 = 1.294. Therefore, you cannot reduce or magnify from one U.S. format to the next higher or lower without leaving an empty margin, which is rather inconvenient.

Common North American paper sizes


in × in

mm × mm



8.5 × 11

215.9 × 279.4



8.0 × 10.5

203.2 × 266.7



8.5 × 14

215.9 × 355.6


Junior Legal

8.0 × 5.0

203.2 × 127



17 × 11

432 × 279



11 × 17

279 × 432



[edit] History and adoption

The historic origins of the 216 × 279 mm U.S. Letter format, and in particular its rationale, seem rather obscure. The American Forest and Paper Association argues that the dimension originates from the days of manual paper making, and that the 11 inch length of the page is about a quarter of "the average maximum stretch of an experienced vatman's (a worker who washes, dyes, cooks, or chemically treats products in a vat) arms." However, this does not explain the width or aspect ratio.

The earliest documented attempts to standardize U.S. paper format used a completely different format. On 28th March 1921, the U.S. Secretary of Commerce (Herbert Hoover – later to become the 31st president of the USA in 1929) declared a 203 × 267 mm format (Government-Letter) to be the standard for his department. It apparently was to enable discounts from the purchase of paper for schools, but more likely due to the standard use of trimming books (after binding) and paper from the standard letter size paper to produce consistency and allow "bleed" printing.

It was adopted on 14th September 1921 by the Permanent Conference on Printing (established by General Dawes, first director of the Bureau of the Budget) as the general U.S. government letterhead standard. It is still used in the United States and Canada for children's writing. The name "government-letter" was given by The Institute of Electrical and Electronics Engineers’ (IEEE) Printer Working Group.

Herbert Hoover.jpg

(Herbert Hoover was U.S. Secretary of Commerce between 1921-1928, and the 31st President of the USA between 1929-1933. Graduated as a mining engineer and was the chief engineer for the Chinese government before and during the 1900 Boxer Rebellion.)

Independent of that, on 30th March 1921 a Committee on the Simplification of Paper Sizes consisting of printing industry representatives was appointed to work with the Bureau of Standards. It recommended standard basic sizes of 432 × 559 mm (17 × 22 in), 432 × 711 mm (17 × 28 in), 483 × 610 mm (19 × 24 in), 559 × 864 mm (22 × 34 in), 711 × 864 mm (28 × 34 in), and 610 × 914 mm (24 × 36 in).

What became known later as the U.S. Letter format is just the first of these basic sizes halved. One hypothesis for the origin of this format series is that it was derived from a then typical mold size used in the production of hand-made paper. “It does not appear, even in the selection of 8 1/2 × 11 inch size paper, that any special analysis was made to prove that this provided an optimum size for a commercial letterhead” [Arthur D. Dunn: Notes on the standardization of paper sizes 1972 ( ]

It appears that this standard was just a commercial compromise at the time to reduce inventory requirements without requiring significant changes to existing production equipment. The Hoover standard (Government-Letter) remained in force until the government declared in January 1980 the Letter format (8.5 in × 11 in or 215.9 mm × 279.4 mm) to be the new official paper format for U.S. government offices.

The reason for this is because, in later years, as photocopy machines proliferated, citizens wanted to make photocopies of government forms, but the machines did not generally have this size paper in their bins. President Jimmy Carter’s administration therefore had the U.S. government switch to regular letter size format (8 1⁄2 in × 11 in or 215.9 mm × 279.4 mm).

The Government-Letter size is still commonly used in spiral-bound notebooks and the like, a result of trimming from the current letter dimensions.

[edit] The Canadian standard (P Series)

The Canadian standard CAN 2-9.60M “Paper Sizes for Correspondence” defines the six formats:

  • P1 (560 × 860 mm) Ratio = 1.5357…
  • P2 (430 × 560 mm) Ratio = 1.3023…
  • P3 (280 × 430 mm) Ratio = 1.5357…
  • P4 (215 × 280 mm) Ratio = 1.3023…
  • P5 (140 × 215 mm) Ratip = 1.5357…
  • P6 (107 × 140 mm) Ratio = 1.3084…

These are just the U.S. sizes rounded to the nearest half centimetre (P4 ~ U.S. Letter, P3 ~ U.S. Ledger). This Canadian standard was introduced in 1976, even though the Ontario Government had already introduced the ISO A series formats in 1972. Even though these Canadian paper sizes look somewhat like a pseudo-metric standard, they still suffer from the two major inconveniences of the U.S. formats, namely they have no common height/width ratio, so therefore suffer with scaling and halving of sizes unlike the 1:√2 ratio of ISO 216, and the sizes of these papers differ significantly from those the rest of the world uses.

[edit] PA series

A transitional size called PA4 (210 mm × 280 mm or 8.27 in × 11.02 in) was proposed for inclusion into the ISO 216 standard in 1975. It has the height of Canadian P4 paper (215 mm × 280 mm, about 8½ in × 11 in) and the width of international A4 paper (210 mm × 297 mm or 8.27 in × 11.69 in). The table below shows how this format can be generalized into an entire format series.

PA4-based series


mm × mm



840 × 1120



560 × 840



420 × 560



280 × 420



210 × 280



140 × 210



105 × 140



70 × 105



52 × 70



35 × 52



26 × 35


The PA formats did not end up in ISO 216, because the committee felt that the set of standardized paper formats should be kept to the minimum necessary. However, PA4 remains of practical use today. In landscape orientation, it has the same 4:3 aspect ratio as the displays of traditional TV sets, some computer displays and data projectors. PA4, with appropriate margins, is therefore a good choice as the format of presentation slides.

PA4 is also a useful compromise between A4 and US/Canadian Letter sizes. Hence it is used today by many international magazines, because it can be printed easily on equipment designed for either A4 or US Letter.

[edit] ANSI paper sizes

The American National Standards Institute adopted ANSI/ASME Y14.1 which defined a regular series of paper sizes based upon the de facto standard 8 1⁄2 in × 11 in (215.9 mm × 279.4 mm) "letter" size which it assigned "ANSI A". The new standard specifies how to use the ISO A0−A4 formats for technical drawings in the U.S.

Technical drawings usually have a fixed drawing scale (e.g., 1:100 means that one meter is drawn as one centimetre), therefore it is not easily possible to resize technical drawings between U.S. and standard paper formats. As a result, internationally operating U.S. corporations increasingly find it more convenient to abandon the old ANSI Y14.1 formats and prepare technical drawings for ISO paper sizes, like the rest of the world.

This series also includes "ledger"/"tabloid" as "ANSI B". This series is somewhat similar to the ISO standard in that cutting a sheet in half would produce two sheets of the next smaller size.

Unlike the ISO standard, however, the arbitrary aspect ratio forces this series to have two alternating aspect ratios. To wit, "Letter" (8½" × 11", or ANSI A) is less elongated than A4, while "Ledger/Tabloid" (11" × 17", or ANSI B) is more elongated than A3. The ANSI series is shown below.

With care, documents can be prepared so that the text and images fit on either ANSI or their equivalent ISO sheets at 1:1 reproduction scale.

Name in × in mm × mm Ratio Alias Similar ISO A size
ANSI A 8.5 × 11 216 × 279 1.2941 Letter A4
ANSI B 11 × 17 279 × 432 1.5455 Ledger Tabloid A3
ANSI C 17 × 22 432 × 559 1.2941 A2
ANSI D 22 × 34 559 × 864 1.5455 A1
ANSI E 34 × 44 864 × 1118 1.2941 A0

Other, larger sizes continuing the alphabetic series illustrated above exist, but it should be noted that they are not part of the series per se, because they do not exhibit the same aspect ratios.

For example, Engineering F size (28 in × 40 in or 711.2 mm × 1,016.0 mm) also exists and is commonly required for NAVFAC (United States Naval Facilities Engineering Command) drawings, but is generally less commonly used, as are G, H, ... N size drawings. G size is 22 1⁄2 in (571.5 mm) high, but variable width up to 90 in (2,286 mm) in increments of 8 1⁄2 in (215.9 mm), i.e., roll format.

H and larger letter sizes are also roll formats. Such sheets were at one time used for full-scale layouts of aircraft parts, wiring harnesses and the like, but are slowly being phased out, due to widespread use of computer-aided design (CAD) and computer-aided manufacturing (CAM).

Some visual arts fields also continue to use these paper formats for large-scale printouts, such as for displaying digitally painted character renderings at life-size as references for makeup artists and costume designers, or to provide an immersive landscape reference.

ANSI papaer size.png

[edit] Architectural sizes

In addition to the ANSI system as listed above, there is a corresponding series of paper sizes used for architectural purposes. This series also shares the property that bisecting each size produces two of the size below, with alternating aspect ratios.

It may be preferred by North American architects because the aspect ratios (4:3 and 3:2) are ratios of small integers, unlike their ANSI (or ISO) counterparts. Furthermore, the aspect ratio 4:3 matches the traditional aspect ratio for computer displays. The architectural series, usually abbreviated "Arch", is shown below:

Name in × in mm × mm Ratio
Arch A 9 × 12 229 × 305 3:4
Arch B 12 × 18 305 × 457 2:3
Arch C 18 × 24 457 × 610 3:4
Arch D 24 × 36 610 × 914 2:3
Arch E 36 × 48 914 × 1219 3:4
Arch E1 30 × 42 762 × 1067 5:7
Arch E2 26 × 38 660 × 965 13:19
Arch E3 27 × 39 686 × 991 9:13

= ARCH paper sizes.png

The adoption of the metric system in the USA =

The United States has been officially on the metric system since 1975. The 'Metric Conversion Act' is an Act of Congress that U.S. President Gerald Ford signed into law on December 23, 1975. It declared the Metric system as, "the preferred system of weights and measures for United States trade and commerce". However, it permitted the use of United States customary units in non-business activities.

The Act also established the government agency of United States Metric Board (USMB) with representatives from scientific, technical, and educational institutions, as well as state and local governments to plan, coordinate, and educate the American people for the metrication of the United States, and to encourage metrication.

All About Metric.jpg

USMB published various educational materials including this 18-page booklet titled All About Metric, printed in 1982.

The existence of The USMB was short lived though - from 1975 to 1982, ending when President Ronald Reagan abolished it, largely on the recommendation of Frank Mankiewicz (journalist and president of National Public Radio in 1981) who encouraged Lyn Nofziger, (President Reagan's assistant for political affairs), to persuade President Reagan to dissolve the board, believing the system was harming the country.

Overall, the board made little impact on implementing the metric system in the United States, but did "educate the American people about the meaning of the Metric system in everyday life", (taken from President Ronald Reagan's letter to Louis Polk, Chairman of the USMB, on 9 March 1982, thanking him for his efforts.)

Just before it dissolved — officially, on 30 September 1982 — the USMB issued the 44-page U.S. Metric Board Summary Report — July 1982, summarizing its four years of activities. Among other things, it includes a list of findings and recommendations, with these main points (for the explanation of each, read the report):



The Summary Report also includes statements from each USMB's 17 members, providing their perspectives on metrication; a detailed summary of USMB activities; the metrication status of each federal agency; and a summary of each state's metric conversion status.

It also includes a brief summary of USMB expenditures and a bibliography of USMB publications.

Congress still recognise the necessity of the United States’ conformance with international standards for trade, and included new encouragement for U.S. industrial metrication in the 'Omnibus Trade and Competitiveness Act of 1988. This legislation amended the Metric Conversion Act of 1975 and designates the metric system as the "...preferred system of weights and measures for United States trade and commerce.” The legislation states that the Federal Government has a responsibility to assist industry, especially small business, as it voluntarily converts to the metric system of measurement.

[edit] the problems of using N.A. Paper sizes

Both the “Letter” and “Legal” format could easily be replaced by A4, “Executive” (if it is really needed) by B5, and “Ledger/Tabloid” by A3. Similarly, the A–E formats can be replaced by A4–A0.

It can be hoped and expected that with the continuing introduction of the metric system in the United States, the ISO paper formats will eventually replace non-standard paper formats. Conversion to A4 as the common business letter and document format in North America would not be too difficult, as practically all modern software, copying machines, and laser printers sold today in the U.S. already support A4 paper as a standard feature.

Users of photocopiers outside the U.S. and Canada usually take it for granted that the machine is able to enlarge A4 → A3 or reduce A3 → A4, the two paper formats usually kept in machines with two paper trays. When they use a copier in North America, it often comes as a disappointing surprise when they find out that magnifying an entire page is not a function available. The absence of this useful capability is a direct result of the unfortunate design of the U.S. paper formats.

North American copiers usually also have two or more paper trays, but these are mostly used for the two very similar “Letter” and “Legal” formats, wasting the opportunity of offering a highly useful magnifying capability. Any enlarging of a “Letter” page onto “Legal” paper will always chop off margins and is therefore of little use.

The Legal format itself is rarely used, the notion that it is for “legal” work is a popular myth; the vast majority of U.S. legal documents actuall use the “Letter” format. Some copiers also offer in addition or instead the next larger “Ledger” format, but that again has a different aspect ratio and will therefore change the margins of a document during magnification or reduction.

Based on the experience from the introduction of ISO paper formats in other industrialized countries at various points during the 20th century, it becomes clear that this process needs to be initiated by a political decision to move all government operation to the new paper format system. History shows that the commercial world then gradually and smoothly adopt the new government standard for office paper within about 10–15 years.

It would not be a major operation to do this in the U.S. and Canada, especially considering that most standard software and office machines are already prepared for A4. However, such a project can succeed only if the national executive has the political will to accomplish it. The transition period of about a decade is necessary to avoid expensive equipment replacement costs for printers, especially those with older large rotary presses that were not yet designed to be easily retooled for ISO paper sizes.

It is advised that if a company/organisation is to purchase new office or printing equipment in North America, it would be wise to pay attention to whether the equipment is suitable for use with A4 paper.

The dominance of the “Letter” format instead of ISO A4 as the common laser-printer paper format in North America causes a lot of problems in daily international document exchange with the USA and Canada. ISO A4 is 6 mm less wide but 18 mm higher than the U.S. “Letter” format. Word processing documents with an A4 layout can often not be printed without loss of information on “Letter” paper or require you to reformat the text, which will change the page numbering.

“Letter” format documents printed outside North America either shows too much white space on the top or bottom of the page or the printer refuses to operate as “Letter” format paper has been selected by the software but is not available. A4 size documents have to be copied or printed with a 94% magnification factor to fit on the 6% less tall “Letter” paper, and “Letter” documents have to be printed with 97% size to fit on the 3% less wide A4 format.

Universities in the U.S. increasingly use A4 size paper in laser printers and library copying machines, because most conferences outside North America require papers to be submitted in A4 format and many journals and conference proceedings are printed in A4 format.

The three-hole 108-mm filing system widely used in the U.S. is not compatible with the two-hole 80-mm ISO system used in most other countries. The three-hole system could of course also be used on A4 pages, but many files with a three-hole mechanism are only designed for U.S. “Letter” sheets and are not tall enough to reliably protect A4 pages. Another disadvantage of the three-hole system is that it is not suitable for storing formats smaller than U.S. “Letter”.

The U.S. Postal Service standard-size range for first-class or single piece third-class mail weighing up to 28 g includes ISO C6 and DL envelopes. The U.S. currently use quite a large number of envelope formats.

[edit] Calculating Weights

The U.S. paper industry has managed to come up with an odd way of specifying the density of paper. Instead of providing you with the obvious quotient of mass per area (e.g., in grams per square meter, ounces per square yard, etc, they specify the total mass M of a ream of N pages of some size X×Y.

This means, you have to know four values in order to understand how to calculate the (scalar) density of the paper. For example “20 lb paper” can mean that a ream of 500 pages in format 24×36 in has a total mass of 20 pounds. These ream sizes of 500 × 24 in × 36 in = 278.70912 m² are somewhat typical in newsprint applications but not universal, as 17×22 in, 25×38 in and other reference sheet sizes are used as well.

With 453.59237 g/lb and 278.70912 m²/ream, you get roughly 1 lb/ream = 1.63 g/m² for this particular ream size. It can be very problematic if you have to do these conversions yourself.

[edit] Supply of ISO 216 paper in North American

Although it is still rarely advertised, ISO A4 laser printer and copying paper, as well as suitable files and folders, are available today from many U.S. office supply companies. A4 paper and supplies have been regularly ordered in the U.S. for many years, especially by companies and organizations with a lot of international correspondence, including patent lawyers, diplomats, universities, and some government agencies.

Many of the larger stationery chains do offer at least one type of A4 paper in their catalogues. Often the only type of A4 paper available is a higher-quality brand: the type of paper one might prefer for important documents, such as international patent applications.

If the suppliers or shop assistant are unfamiliar with “A4 paper”, try asking for “210 mm × 297 mm”, “8 1/4 in × 11 3/4 in”, “international size”, or “European size” paper.

[edit] Note:

If you live in the U.S. and have never been abroad, you might not be aware that paper and accessories in the North-American sizes are not commonly available outside the U.S. or Canada. They are very difficult to obtain in any other country and the only practical way to get U.S. “Letter” is to cut one of the next larger available sizes (usually B4, A3 or RA4).

If you send documents to any other country, your use of A4 will greatly ease the handling and filing of your documents for the recipient. If you design software that might be used globally, please keep in mind that the vast majority of laser printer users will print onto A4 paper. Therefore, always make A4 the default setting and the first selection choice in your printing user interface. Remember that it is the paper format used by about 95% of the people on this planet.

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