Grammage and basis weight, in the pulp and paper industry, are the

area density The area density (also known as areal density, surface density, superficial density, areic density, column density, or density thickness) of a two-dimensional object is calculated as the mass per unit area. The SI derived unit is the "kilogram p ...

of a

paper Paper is a thin sheet material produced by mechanically or chemically processing cellulose fibres derived from wood, Textile, rags, poaceae, grasses, Feces#Other uses, herbivore dung, or other vegetable sources in water. Once the water is dra ...

product, that is, its

mass Mass is an Intrinsic and extrinsic properties, intrinsic property of a physical body, body. It was traditionally believed to be related to the physical quantity, quantity of matter in a body, until the discovery of the atom and particle physi ...

per unit of

area Area is the measure of a region's size on a surface. The area of a plane region or ''plane area'' refers to the area of a shape or planar lamina, while '' surface area'' refers to the area of an open surface or the boundary of a three-di ...

. Two ways of expressing the area density of a paper product are commonly used: * Expressed in

gram The gram (originally gramme; SI unit symbol g) is a Physical unit, unit of mass in the International System of Units (SI) equal to one thousandth of a kilogram. Originally defined in 1795 as "the absolute Mass versus weight, weight of a volume ...

s (g) per

square metre The square metre ( international spelling as used by the International Bureau of Weights and Measures) or square meter ( American spelling) is the unit of area in the International System of Units (SI) with symbol m2. It is the area of a square ...

(g/m²), regardless of its thickness ( caliper)International Standard ISO 536: Paper and board – Determination of grammage.

International Organization for Standardization The International Organization for Standardization (ISO ; ; ) is an independent, non-governmental, international standard development organization composed of representatives from the national standards organizations of member countries. M ...

, Geneva. (known as ''grammage''). This is the measure used in most parts of the world. It is often notated as ''gsm'' on paper product labels and spec sheets. * Expressed in terms of the mass per number of sheets of a specific

paper size Paper size refers to Technical standard, standardized dimensions for sheets of paper used globally in stationery, printing, and technical drawing. Most countries adhere to the ISO 216 standard, which includes the widely recognized A series ( ...

(known as ''basis weight''). The convention used in the United States and a few other countries using US-standard paper sizes is pounds (lb) per ream of 500 (or in some cases 1000) sheets of a given (raw, still uncut) basis size. The traditional British practice is pounds per ream of 480, 500, 504, or 516 sheets of a given basis size. Japanese paper is expressed as the weight in

kilogram The kilogram (also spelled kilogramme) is the base unit of mass in the International System of Units (SI), equal to one thousand grams. It has the unit symbol kg. The word "kilogram" is formed from the combination of the metric prefix kilo- (m ...

s (kg) per 1,000 sheets.

Grammage

In the

metric system The metric system is a system of measurement that standardization, standardizes a set of base units and a nomenclature for describing relatively large and small quantities via decimal-based multiplicative unit prefixes. Though the rules gover ...

, the mass per unit area of all types of paper and paperboard is expressed in terms of grams per square metre (g/m²). This quantity is commonly called ''

grammage Grammage and basis weight, in the pulp and paper industry, are the area density of a paper product, that is, its mass per unit of area. Two ways of expressing the area density of a paper product are commonly used: * Expressed in grams (g) per s ...

'' in both English and French, though printers in most English-speaking countries still refer to the "

weight In science and engineering, the weight of an object is a quantity associated with the gravitational force exerted on the object by other objects in its environment, although there is some variation and debate as to the exact definition. Some sta ...

" of paper. :

\text = \frac

Typical office paper has , therefore a typical A4 sheet ( of a square metre) weighs . The abbreviation "gsm" instead of the standard g/m² symbol is also widely encountered in

English-speaking countries The English-speaking world comprises the 88 countries and territories in which English is an official, administrative, or cultural language. In the early 2000s, between one and two billion people spoke English, making it the largest language ...

. Typically grammage is measured in

paper mill A paper mill is a factory devoted to making paper from vegetable fibres such as wood pulp, old rags, and other ingredients. Prior to the invention and adoption of the Fourdrinier machine and other types of paper machine that use an endless belt ...

on-line by a quality control system and verified by laboratory measurement.

Basis weight

Basis weight of paper is the density of paper expressed in terms of the mass (in pound) of a ream of paper of given dimensions and a sheet count. The American and the traditional British systems are largely the same, with only minor differences: the paper dimensions and the sheet count are different.

United States

In the US system, the weight is specified in avoirdupois pounds and the sheet count of a paper ream is usually 500 sheets. However, the mass specified is not the mass of the ream that is sold to the customer. Instead, it is the mass of the uncut "basis ream" in which the sheets have some larger size (parent size). Often, that is a size used during the manufacturing process before the paper is cut to the dimensions in which it is sold. So, to compute the mass per area, one must know * the mass of the basis ream, * the number of sheets in that ream, and * the dimensions of an "uncut" sheet in that ream. The standard dimensions and sheet count of a ream vary according to the type of paper. These "uncut" basis sizes are not normally labelled on the product, are not formally standardized, and therefore have to be guessed or inferred somehow from trading practice. Historically, this convention is the product of pragmatic considerations such as the size of a sheet mold. By using the same basis sheet size for the same type of paper, consumers can easily compare papers of differing brands. Twenty-pound bond paper is always lighter and thinner than 32-pound bond, no matter what its cut size, and 20-pound bond ''letter size'' and 20-pound bond ''legal size'' papers are the same weight paper with a different cut size. However, a sheet of common copy paper that has a basis weight of does not have the same mass as the same size sheet of coarse paper (newsprint). In the former case, the standard ream is 500 sheets of paper, and in the latter, 500 sheets of paper. Here are some basic ream sizes for various types of paper. Units are inches except where noted. : Sheets can be cut into four sheets, a standard for business stationery known conventionally as ''letter sized paper''. So, the ream became commonly used. The book-paper ream developed because such a size can easily be cut into sixteen

book size The size of a book is generally measured by the height against the width of a leaf, or sometimes the height and width of its cover. A series of terms is commonly used by libraries and publishers for the general sizes of modern books, ranging from ...

d sheets without significant waste (nominally before trimming and binding). Early newsprint presses printed sheets in size, and so the ream dimensions for newsprint became , with 500 sheets to a ream. Newsprint was made from ground wood pulp, and ground wood hanging paper (

wallpaper Wallpaper is used in interior decoration to cover the interior walls of domestic and public buildings. It is usually sold in rolls and is applied onto a wall using wallpaper paste. Wallpapers can come plain as "lining paper" to help cover uneve ...

) was made on newsprint machines. Newsprint was used as wrapping paper, and the first paper bags were made from newsprint. The newsprint ream standard also became the standard for packaging papers, even though in packaging papers

kraft Kraft Foods Group, Inc. was an American food manufacturing and processing conglomerate (company), conglomerate, split from Kraft Foods Inc. on October 1, 2012, and was headquartered in Chicago, Illinois. It became part of Kraft Heinz on July ...

pulp, rather than ground wood, was used for greater strength. Paper weight is sometimes stated using the " #" symbol. For example, "20#" means "20 pounds per basis ream of that kind of paper". When the density of a ream of paper is given in pounds, it is often accompanied by its "M weight" (M is 1000 in

Roman numerals Roman numerals are a numeral system that originated in ancient Rome and remained the usual way of writing numbers throughout Europe well into the Late Middle Ages. Numbers are written with combinations of letters from the Latin alphabet, eac ...

). The M weight is the weight (in pounds) of 1000 cut sheets. Paper suppliers will often charge by M weight, since it is always consistent within a specific paper size, and because it allows a simple weight calculation for shipping charges. For example, a 500-sheet ream of 20# copy paper may be specified "10 M". 1000 cut sheets (or two reams) will weigh , half of the four reams of cut paper resulting from the 20# basis ream of paper.

United Kingdom

Overview of the traditional British system

Like the American system, the traditional British system also involves the use of basis weight to express the area density of paper (and, indirectly, paper thickness) in the course of buying and selling paper. The British paper industry exclusively used basis weight before 1968. In the traditional British system, basis weight is also expressed in terms of the weight of an imaginary ream of paper of a certain size. The underlying concept is that a ream of paper of the stated paper size and of the same thickness as the paper the parties are dealing with would have the stated weight. The weight is expressed in pound. As to paper sizes (basis sizes), they can, theoretically, be any sizes, but, by custom, a number of common sizes emerged. In the 1960s, even the metric A1 and A2 had been used as basis sizes alongside the British ones. The following are common British basis sizes (sizes of British uncut paper): One ream in the context of basis weight (basis ream) can be 480 sheets, 500 sheets, 504 sheets, or 516 sheets: there is no fixed rule on when a certain definition was applied; however, starting from the 1950s, the trend of moving towards 500 sheets emerged. Basis weight is commonly expressed in terms of pound per ream of paper of a certain size, in the format of '

umber Umber is a natural earth pigment consisting of iron oxide and manganese oxide; it has a brownish color that can vary among shades of yellow, red, and green. Umber is considered one of the oldest pigments known to humans, first used in the Ajant ...

b aper size (e. g., '21lb large post' ('21 pounds per ream of large post paper')). Since there are basis reams of different sizes, unless the context leaves no room for ambiguity, the number of sheets in the basis ream is also given after the paper size to avoid misunderstanding: in such case, basis weight is expressed in the format of '

b aper size umber of sheets of paper in the basis ream, such as '21lb large post 480' ('21 pounds per 480‑sheet ream of large post paper'). In the United Kingdom, '#' has never been used to express paper weight because it is called 'hash', instead of 'pound', in British English. Demy traditionally plays the role of the default basis size for expressing basis weights: in the British paper industry, there was a device, called 'demy scale', that was used to measure the weights of different paper samples in pound per ream of demy paper (480‑sheet, 500‑sheet, and 516‑sheet reams). Below is a list of commonBased on the basis weights mentioned in the paper‑related advertisements and articles in the following newspapers and paper‑industry magazines published during the days when the British paper industry exlcusively used basis weights: * Advertisement by J. Moore
page 5
15th December, 1853 edition, ''The Sydney Morning Herald'' * 'London School Board', page 69
March, 1887 edition
''The Stationery Trade Review'' * Page
2434
an
87
25th January, 1892 edition, ''The Printing World''
Advertisement immediately after page 40
March–April, 1892 edition, ''The British Printer'' * Supplement immediately afte
page 106
an
page 122
5th March, 1892 edition, ''The Printing World'' * Advertisement
between pages 208 and 209
an
on page 222
25th May, 1892 edition, ''The Printing World''
Page 362
25th August, 1892 edition, ''The Printing World''
Page 461
25th October, 1892 edition, ''The Printing World''
Respective advertisements from John Muir and Strong & Hanbury on two unnumbered pages of the advertisement supplement immediately after page 452the red-inked page 37 after page 452
an
the advertisement from Alexander Cowan & Sons on a red-inked page 12 of a certain advertisement supplement after page 452
November–December, 1893 edition, ''The British Printer''
Page 20 of the advertisement supplement
January–February, 1897 edition, ''The British Printer'' * Pages 29–32
March, 1906 edition
''Tanner's Trade Circular'' * Pages 50–52 and the back of the back cover
April, 1906 edition
''Tanner's Trade Circular'' * Pages 57, 59, 67, and 68
May, 1906 edition
''Tanner's Trade Circular'' * Page 70
June, 1906 edition
''Tanner's Trade Circular'' * Pages 114, 115, 122, 131, and 132
July, 1906 edition
''Tanner's Trade Circular'' * Pages 147 and 148
August, 1906 edition
''Tanner's Trade Circular'' * Back of the back cover
September, 1906 edition
''Tanner's Trade Circular'' * Back of the back cover
October, 1906 edition
''Tanner's Trade Circular'' * Page 183 and the back of the back cover
November, 1906 edition
''Tanner's Trade Circular'' * Back of the back cover and pages 202 and 219
December, 1906 edition
''Tanner's Trade Circular'' * Pages 14 and 22 and the back of the back cover
February, 1907 edition
''Tanner's Trade Circular'' * Back of the cover; pages 26, 27, 38, and 44–47; and the back of the back cover
March, 1907 edition
''Tanner's Trade Circular'' * Back of the cover and pages 51 and 60–70
April, 1907 edition
''Tanner's Trade Circular'' * Pages 75, 77, 82, 93, and 94
May, 1907 edition
''Tanner's Trade Circular'' * Back of the cover and pages 147, 149, 158, and 165–167
August, 1907 edition
''Tanner's Trade Circular'' * Pages 229, 238, and 239
November, 1907 edition
''Tanner's Trade Circular'' * Back of the cover and the back of the back cover
December, 1907 edition
''Tanner's Trade Circular'' * Back cover
July, 1908 edition
''Tanner's Trade Circular'' * Back of the back cover and pages 3, 5, 12, and 14
January, 1910 edition
''Tanner's Trade Circular'' * Back of the cover; pages 45, 47, and 54; and the back of the back cover
March, 1910 edition
''Tanner's Trade Circular'' * Pages 43, 52, and 62
April, 1910 edition
''Tanner's Trade Circular'' * Back of the cover; pages 123, 125, 128, 132, and 138; and the back cover
July, 1910 edition
''Tanner's Trade Circular'' * Pages 148, 154, and 155
August, 1910 edition
''Tanner's Trade Circular'' * Pages 163, 168, 174, and 175
September, 1910 edition
''Tanner's Trade Circular'' * Pages 181 and 188
October, 1910 edition
''Tanner's Trade Circular'' * Pages 214 and 218
November, 1910 edition
''Tanner's Trade Circular'' * Pages 4 and 6 and the back of the back cover
January, 1911 edition
''Tanner's Trade Circular'' * Pages 36 and 37
February, 1911 edition
''Tanner's Trade Circular'' * Pages 43, 52, 56, and 57
March, 1911 edition
''Tanner's Trade Circular'' * Page 69
April, 1911 edition
''Tanner's Trade Circular'' * Pages 82 and 96
May, 1911 edition
''Tanner's Trade Circular'' * Page 146
August, 1911 edition
''Tanner's Trade Circular'' * Page 172
September, 1911 edition
''Tanner's Trade Circular'' * Pages 194 and 195 and the back cover
October, 1911 edition
''Tanner's Trade Circular'' * Pages 205, 206, and 226
November, 1911 edition
''Tanner's Trade Circular'' * Pages 238 and 239
December, 1911 edition
''Tanner's Trade Circular'' * Page 28
February, 1912 edition
''Tanner's Trade Circular'' * Pages 46, 48, 58, and 60
March, 1912 edition
''Tanner's Trade Circular'' * Page 82
April, 1912 edition
''Tanner's Trade Circular'' * Back of the back cover and page 86
May, 1912 edition
''Tanner's Trade Circular'' * Pages 114 and 118
June, 1912 edition
''Tanner's Trade Circular'' * Page 121
July, 1912 edition
''Tanner's Trade Circular'' * Page 182
October, 1912 edition
''Tanner's Trade Circular'' * Page 26
February, 1913 edition
''Tanner's Trade Circular'' * Page 35
March, 1913 edition
''Tanner's Trade Circular'' * Pages 74 and 75
May, 1913 edition
''Tanner's Trade Circular'' * Pages 116 and 122 and the back cover
August, 1913 edition
''Tanner's Trade Circular'' * Pages 147, 148, and 154
October, 1913 edition
''Tanner's Trade Circular'' * Page 179
December, 1913 edition
''Tanner's Trade Circular'' * Page 37
March, 1914 edition
''Tanner's Trade Circular'' * Page 58 and the back of the back cover
April, 1914 edition
''Tanner's Trade Circular'' * Pages 77–79
May, 1914 edition
''Tanner's Trade Circular'' * Pages 26, 82, 92, and 98 and the back of the back cover
June, 1914 edition
''Tanner's Trade Circular'' * Page 100
July, 1914 edition
''Tanner's Trade Circular'' * Page 114
August, 1914 edition
''Tanner's Trade Circular'' * Pages 146 and 152
December, 1914 edition
''Tanner's Trade Circular'' * Pages 8, 12, and 14
January, 1922 edition
''Tanner's Trade Circular'' * Pages 18, 26, and 30
February, 1922 edition
''Tanner's Trade Circular'' * Pages 34, 38, and 40 and the back of the back cover
March, 1922 edition
''Tanner's Trade Circular'' * Pages 50, 51, and 114
April, 1922 edition
''Tanner's Trade Circular'' * Pages 115 and 126
August, 1922 edition
''Tanner's Trade Circular'' * Pages 146, 147, and 149
October, 1922 edition
''Tanner's Trade Circular'' * Page 178 and the back of the back cover
December, 1922 edition
''Tanner's Trade Circular'' * Pages 70, 74, and 76
May, 1923 edition
''Tanner's Trade Circular'' * Pages 120, 121, and 124
August, 1923 edition
''Tanner's Trade Circular'' * Page 138
September, 1923 edition
''Tanner's Trade Circular'' * Pages 152 and 154 and the back cover
October, 1923 edition
''Tanner's Trade Circular'' * Back of the cover and pages 178, 184, 185, and 188
December, 1923 edition
''Tanner's Trade Circular'' * Back of the cover and pages 4, 8, 9, and 12
January, 1924 edition
''Tanner's Trade Circular'' * Back of the back cover
April, 1952 edition
''Highlight'' * Pages 49 and 52
April, 1953 edition
''Highlight'' * Back of the back cover
July, 1953 edition
''Highlight'' * Page 75
October, 1953 edition
''Highlight'' * Back of the back cover
January, 1954 edition
''Highlight'' * Page 4
April, 1954 edition
''Highlight'' * Back of the cover and page 17
July, 1954 edition
''Highlight'' * Page 33
October, 1954 edition
''Highlight'' * Back of the cover
January, 1955 edition
''Highlight'' * Page 11
April, 1955 edition
''Highlight'' * Back of the back cover
July, 1955 edition
''Highlight'' * Back of the cover and page 33
October, 1955 edition
''Highlight'' * Back of the back cover
January, 1956 edition
''Highlight'' * Page 11 and the back of the back cover
April, 1956 edition
''Highlight'' * Back of the cover and the back of the back cover
July, 1956 edition
''Highlight'' * Page 28
October, 1956 edition
''Highlight'' * Back of the back cover
January, 1957 edition
''Highlight'' * Back of the cover and page 3
April, 1957 edition
''Highlight'' * Back of the back cover
October, 1958 edition
''Highlight'' * Page 11
January, 1959 edition
''Highlight'' * Back of the cover
October, 1959 edition
''Highlight'' * Page 10
January, 1960 edition
''Highlight'' * Pages 15, 17, and 23 and the back of the back cover
April, 1960 edition
''Highlight'' * Back of the cover
July, 1960 edition
''Highlight'' * Page 45 and the back of the back cover
October, 1960 edition
''Highlight'' * Page 3 and the back of the back cover
July, 1961 edition
''Highlight'' * Back of the cover and page 11
January, 1962 edition
''Highlight'' * Page 3
April, 1962 edition
''Highlight'' * Page 11 and the back of the back cover
April, 1963 edition
''Highlight'' * Page 11 and the back of the back cover
October, 1963 edition
''Highlight'' * Back of the back cover
July, 1964 edition
''Highlight'' * Page 11
July, 1965 edition
''Highlight'' * Back of the cover and the back of the back cover
January, 1966 edition
''Highlight'' * Back of the cover
January, 1967 edition
''Highlight'' * Page 3
July, 1967 edition
''Highlight'' * Page 3
October, 1967 edition
''Highlight'' basis weights of paper stocked by British paper merchants:

Conversion between British basis weights, American basis weights, and grammage

It is possible to convert between different basis weights – both British and American – and grammage using different conversion formulae. To convert between the basis weights of different paper with the same basis‑ream size (e. g., from to ), the following formula can be employed: Area of one sheet of paper in the target ream × Weight of the source ream ÷ Area of one sheet of paper in the source ream To convert between the basis weights of different paper with different basis‑ream sizes (e. g., from to ), the relevant formula is below: (Number of sheets of paper in the target ream × Area of one sheet of paper in the target ream) × Weight of the source ream ÷ (Number of sheets of paper in the source ream × Area of one sheet of paper in the source ream) To convert between the basis weights of the same paper with different basis‑ream sizes (e. g., from to ), one may either use the previous formula or the one below: Weight of the source ream × Applicable conversion factor from the table below To convert from a basis weight to its equivalent grammage, the following is the applicable formula: Page 157, ''Paper and Its Uses'' (1939 edition) Weight of the basis ream × 703,125 ÷ Area of one sheet of paper in the basis ream in square inch × Number of sheets of paper in the basis ream To convert from grammage to the equivalent basis weight, the formula below can be used: Area of one sheet of paper in the basis ream in square inch × Number of sheets of paper in the basis ream × Value of gram per square metre ÷ 703,125 Utilising the aforementioned formulae, it is possible to work out the conversion factors for converting between various British and American units of basis weight and the gram per square metre: Using British basis sizes and the 500‑sheet basis‑ream (a traditional British basis‑ream size that coincides with the modern standard definition of 'ream'), and with the help of the aforementioned conversion formulae or conversion factors, it is possible to express the paper weights of different types of paper in everyday life using British units of basis weight: the typical photocopier paper that is used as all‑purpose paper is 17 or 19 (70 or 80gsm); personal and business letter paper, especially that with engraved letterheads, is typically 24–29 (100–120gsm); greetings cards are usually 85–106 (200–250gsm); newspaper paper is typically 15–23 (35–55gsm);Paper GSM Guide
, The Paperbox Limited business cards are usually 128–149 (300–350gsm); two‑ply toilet rolls and paper kitchen towels are 7 (31gsm) (both layers combined) and 17 (40gsm), respectively; and the typical department‑store wrapping paper is commonly 46–65 (50–70gsm). In the traditional British system, large post, double crown, and double imperial are common British basis sizes for writing paper, printing paper and other paper that is not writing or wrapping paper, and wrapping paper, respectively. '500' is omitted because it is clear from the context that a 'ream' is 500 sheets.

Caliper

Paper thickness, or caliper, is a common measurement specified and required for certain printing applications. Since a paper's

density Density (volumetric mass density or specific mass) is the ratio of a substance's mass to its volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' (or ''d'') can also be u ...

is typically not directly known or specified, the thickness of any sheet of paper cannot be calculated by any method. Instead, it is measured and specified separately as its caliper. However, paper thickness for most typical business papers might be similar across comparable brands. If thickness is not specified for a paper in question, it must be either measured or guessed based on a comparable paper's specification. Caliper is usually measured in micrometres (μm), or in the United States also in mils (1 mil = in = 25.4 μm). Commonly, 20-pound

bond paper Bond paper is a high-quality durable writing paper similar to bank paper but having a weight greater than 50 g/m2. The most common weights are 60 g/m2 (16 lb), 75 g/m2 (20 lb) and 90 g/m2 (24 lb). The name comes fro ...

ranges between roughly in thickness. The

paper density Paper density is a paper product's mass per unit volume. The density can be calculated by dividing the grammage of paper (in grams per square metre or "gsm") by its caliper (usually in micrometres, occasionally in mils). The "ISO 534:2011, ...

is calculated by dividing the grammage over the caliper, and is usually expressed in grams per cubic centimetre (g/cm³) to cancel out the mathematical need for

unit conversion Conversion of units is the conversion of the unit of measurement in which a quantity is expressed, typically through a multiplicative conversion factor that changes the unit without changing the quantity. This is also often loosely taken to incl ...

s between

metre The metre (or meter in US spelling; symbol: m) is the base unit of length in the International System of Units (SI). Since 2019, the metre has been defined as the length of the path travelled by light in vacuum during a time interval of of ...

s and micrometres (a conversion factor of 1,000,000).

Notes

References

External links

Understanding Paper Weights

( Staples, Inc.)
M-weight Calculator

Paper Weight Calculator

Paper Weight Conversion GSM to LBS
{{Use dmy dates, date=February 2021 Paper Printing