Grammage and basis weight, in the
pulp and paper
The pulp and paper industry comprises companies that use wood as raw material and produce pulp, paper, paperboard and other cellulose-based products.
Manufacturing process
The pulp is fed to a paper machine where it is formed as a paper web an ...
industry, are the
area density
The area density (also known as areal density, surface density, superficial density, areic density, mass thickness, column density, or density thickness) of a two-dimensional object is calculated as the mass per unit area. The SI derived unit is ...
of a
paper
Paper is a thin sheet material produced by mechanically or chemically processing cellulose fibres derived from wood, rags, grasses or other vegetable sources in water, draining the water through fine mesh leaving the fibre evenly distributed ...
product, that is, its
mass
Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different elementar ...
per unit of
area
Area is the quantity that expresses the extent of a region on the plane or on a curved surface. The area of a plane region or ''plane area'' refers to the area of a shape
A shape or figure is a graphics, graphical representation of an obje ...
. Two ways of expressing grammage 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 one thousandth of a kilogram.
Originally defined as of 1795 as "the absolute weight of a volume of pure wate ...
s (g) per
square meter
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 w ...
(g/m
2), regardless of its thickness (
caliper
A caliper (British spelling also calliper, or in plurale tantum sense a pair of calipers) is a device used to measure the dimensions of an object.
Many types of calipers permit reading out a measurement on a ruled scale, a dial, or a digital dis ...
).
[International Standard ISO 536: Paper and board – Determination of grammage. ]International Organization for Standardization
The International Organization for Standardization (ISO ) is an international standard development organization composed of representatives from the national standards organizations of member countries. Membership requirements are given in Ar ...
, Geneva. 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 standards govern the size of sheets of paper used as writing paper, stationery, cards, and for some printed documents.
The ISO 216 standard, which includes the commonly used A4 size, is the international standard for paper size. ...
, 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 a
ream
Ream may refer to:
* Paper ream, unit of 500 sheets of paper
* Ream (surname)
* Reamer, tool used to widen a hole
* Ream, West Virginia
* Ream, the name of Rama in the Khmer version of the Ramayana, the Reamker
* Ream National Park, a national pa ...
of 500 (or in some cases 1000) sheets of a given (raw, still uncut) basis size. Japanese paper is expressed as the weight in
kilogram
The kilogram (also kilogramme) is the unit of mass in the International System of Units (SI), having the unit symbol kg. It is a widely used measure in science, engineering and commerce worldwide, and is often simply called a kilo colloquially ...
s (kg) per 1,000 sheets.
Grammage
In the
metric system
The metric system is a system of measurement that succeeded the Decimal, decimalised system based on the metre that had been introduced in French Revolution, France in the 1790s. The historical development of these systems culminated in the d ...
, the mass per unit area of all types of paper and paperboard is expressed in terms of grams per square meter (g/m
2 or gsm). 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 grammage are commonly used:
* Expressed in grams (g) per square meter (g/m2), regardle ...
'' in both
English
English usually refers to:
* English language
* English people
English may also refer to:
Peoples, culture, and language
* ''English'', an adjective for something of, from, or related to England
** English national ide ...
and
French, though printers in most English-speaking countries still refer to the "
weight
In science and engineering, the weight of an object is the force acting on the object due to gravity.
Some standard textbooks define weight as a Euclidean vector, vector quantity, the gravitational force acting on the object. Others define weigh ...
" of paper.
:
Typical office paper has , therefore a typical
A4 sheet ( of a square metre) weighs . The unofficial abbreviation "gsm" instead of the standard "g/m
2" symbol is also widely encountered in
English-speaking countries
The following is a list of English-speaking population by country, including information on both native speakers and second-language speakers.
List
* The European Union is a supranational union composed of 27 member states. The total Engl ...
.
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
In countries that use
America
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
n
paper size
Paper size standards govern the size of sheets of paper used as writing paper, stationery, cards, and for some printed documents.
The ISO 216 standard, which includes the commonly used A4 size, is the international standard for paper size. ...
s, a less verifiable measure known as ''basis weight'' is used in addition to or instead of grammage. The basis weight of paper is the density of paper expressed in terms of the mass of a
ream
Ream may refer to:
* Paper ream, unit of 500 sheets of paper
* Ream (surname)
* Reamer, tool used to widen a hole
* Ream, West Virginia
* Ream, the name of Rama in the Khmer version of the Ramayana, the Reamker
* Ream National Park, a national pa ...
of given dimensions and a sheet count. In the US system, the weight is specified in
avoirdupois
The avoirdupois system (; abbreviated avdp.) is a measurement system of weights that uses pounds and ounces as units. It was first commonly used in the 13th century AD and was updated in 1959.
In 1959, by international agreement, the definiti ...
pounds and the sheet count of a
paper ream
Various measures of paper quantity have been and are in use. Although there are no S.I. units such as quires and bales, there are International Organization for Standardization, ISO''ISO 4046-3:2002 Paper, board, pulps and related terms – Vocab ...
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 a material used in interior decoration to decorate 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" (so t ...
) 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
The second incarnation of Kraft Foods is an American food manufacturing and processing conglomerate, split from Kraft Foods Inc. in 2012 and headquartered in Chicago, Illinois. It became part of Kraft Heinz in 2015.
A merger with Heinz, arra ...
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 500 sheets". When the density of a ream of paper is given in pounds, it is often accompanied by its "M weight". 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.
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 substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematical ...
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
A caliper (British spelling also calliper, or in plurale tantum sense a pair of calipers) is a device used to measure the dimensions of an object.
Many types of calipers permit reading out a measurement on a ruled scale, a dial, or a digital dis ...
. 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
micrometers
The micrometre (American and British English spelling differences#-re, -er, international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American and British English spelling differences# ...
(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 from ...
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, Pap ...
is calculated by
dividing the grammage over the caliper, and is usually expressed in
grams per cubic centimeter (g/cm
3)
to
cancel out
Cancelling out is a mathematics, mathematical process used for removing subexpressions from a mathematical expression, when this removal does not change the meaning or the value of the expression because the subexpressions have equal and oppos ...
the mathematical need for
unit conversion
Conversion of units is the conversion between different units of measurement for the same quantity, typically through multiplicative conversion factors which change the measured quantity value without changing its effects.
Overview
The process ...
s between
meter
The metre (British spelling) or meter (American spelling; see spelling differences) (from the French unit , from the Greek noun , "measure"), symbol m, is the primary unit of length in the International System of Units (SI), though its prefi ...
s and micrometers (a
conversion factor of 1,000,000).
See also
*
Density
Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematical ...
**
Area density
The area density (also known as areal density, surface density, superficial density, areic density, mass thickness, column density, or density thickness) of a two-dimensional object is calculated as the mass per unit area. The SI derived unit is ...
**
Linear density
Linear density is the measure of a quantity of any characteristic value per unit of length. Linear mass density (titer in textile engineering, the amount of mass per unit length) and linear charge density (the amount of electric charge per unit ...
*
Envelope size
An envelope is a common packaging item, usually made of thin, flat material. It is designed to contain a flat object, such as a letter (message), letter or Greeting card, card.
Traditional envelopes are made from sheets of paper cut to one o ...
*
Hole punch
A hole punch, also known as hole puncher, or paper puncher, is an office tool that is used to create holes in sheets of paper, often for the purpose of collecting the sheets in a binder or folder. A ''hole punch'' can also refer to similar t ...
— filing holes
*
Index card
An index card (or record card in British English and system cards in Australian English) consists of card stock (heavy paper) cut to a standard size, used for recording and storing small amounts of discrete data. A collection of such cards e ...
*
Paper and ink testing
*
Photo print sizes Standard photographic print sizes are used in photographic printing. Cut sheets of paper meant for printing photographs are commonly sold in these sizes.
Many nominal and effective sizes are specified in international standard ISO 1008 using mill ...
References
External links
Paper Weight - Conversion Chart(
Staples, Inc.)
M-weight CalculatorPaper Weight CalculatorPaper Weight Conversion GSM to LBS
{{Use dmy dates, date=February 2021
Paper
Printing