Grammage

Template:Short description Template:Redirect 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 square metre (g/m²), regardless of its thickness (caliper) (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 (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 kilograms (kg) per 1,000 sheets.

Grammage

In the metric system, 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 in both English and French, though printers in most English-speaking countries still refer to the "weight" of paper.

$\text{Grammage}=\frac{\text{mass}\text{ (g)}}{\text{length}(\text{m})\times \text{width}(\text{m})}$

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

Typically grammage is measured in paper mill 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 Template:Convert 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 Template:Convert paper, and in the latter, 500 sheets of Template:Convert paper. Here are some basic ream sizes for various types of paper. Units are inches except where noted.

Paper type	Paper size (inches)		Sheets per ream
Bond, writing, ledger	17	× 22	500
Manuscript cover	18	× 31	500
Blotting	19	× 24	500
Box cover	20	× 24	500
Cover	20	× 26	500 or 1000
Watercolour	22	× 30	500
Bristol and tag	Template:Frac	× Template:Frac	500
Tissue	24	× 36	480
Newsprint	24	× 36	500
Hanging, waxing, bag, etc.	24	× 36	500
Book, text, offset	25	× 38	500
Index bristol	Template:Frac	× Template:Frac	500
Paperboard (all types)	12	× 12	1000 (Template:Nowrap per ream)

Sheets Template:Convert can be cut into four Template:Convert sheets, a standard for business stationery known conventionally as letter sized paper. So, the Template:Convert ream became commonly used. The Template:Convert book-paper ream developed because such a size can easily be cut into sixteen Template:Convert book sized sheets without significant waste (nominally Template:Convert before trimming and binding).

Early newsprint presses printed sheets Template:Convert in size, and so the ream dimensions for newsprint became Template:Convert, with 500 sheets to a ream. Newsprint was made from ground wood pulp, and ground wood hanging paper (wallpaper) 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 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). 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# Template:Convert copy paper may be specified "10 M". 1000 cut sheets (or two reams) will weigh Template:Convert, half of the four reams of cut paper resulting from the 20# basis ream of Template:Convert 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):

Common British basis sizes

Note 1: The Italicised writing‑paper and printing‑paper sizes were in use only prior to the 1925 standardisation of writing‑paper and printing‑paper sizes. The 1925 standardisation did not apply to wrapping‑paper sizes. Note 2: The underlined writing‑paper and printing‑paper sizes were in use after the 1925 standardisation but were not adopted as standard sizes by British Standards Institution specification number 730 of 1937. Note 3: The wrapping‑paper sizes marked with ‘*’ were not adopted as standard sizes by British Standards Institution specification number 730 of 1937.
Writing paper
Atlas	26Template:Pprime × 34Template:Pprime
Copy	16Template:SfracTemplate:Pprime × 20Template:Pprime
Double elephant (adopted by British Standards Institution specification number 730 of 1937 but not the 1925 standardisation)	27Template:Pprime × 40Template:Pprime
Double imperial	30Template:Pprime × 44Template:Pprime
Double large post	21Template:Pprime × 33Template:Pprime
Double post (adopted by British Standards Institution specification number 730 of 1937 but not the 1925 standardisation)	19Template:Pprime × 30Template:Pprime (prior to re‑definition by British Standards Institution specification number 730 of 1937, 19Template:Pprime × 30Template:SfracTemplate:Pprime)
Double pott	15Template:Pprime × 25Template:Pprime
Double small demy (known as ‘double demy’ before the 1925 standardisation)	20Template:Pprime × 31Template:Pprime
Double small foolscap (known as ‘double foolscap’ before British Standards Institution specification number 730 of 1937) (‘foolscap’ is sometimes shortened to ‘’cap’ or ‘cap’)	16Template:SfracTemplate:Pprime × 26Template:SfracTemplate:Pprime
Double small royal (known as ‘double royal’ before the 1925 standardisation)	24Template:Pprime × 38Template:Pprime
Elephant	23Template:Pprime × 28Template:Pprime
Imperial	22Template:Pprime × 30Template:Pprime
Large post	16Template:SfracTemplate:Pprime × 21Template:Pprime
Pinched post	14Template:SfracTemplate:Pprime × 18Template:SfracTemplate:Pprime
Post (adopted by British Standards Institution specification number 730 of 1937 but not the 1925 standardisation)	15Template:Pprime × 19Template:Pprime (prior to re‑definition by British Standards Institution specification number 730 of 1937, 15Template:SfracTemplate:Pprime ×19Template:Pprime)
Pott	12Template:SfracTemplate:Pprime × 15Template:Pprime
Sheet‑and‑a‑half small foolscap (known as ‘sheet‑and‑a‑half foolscap’ before British Standards Institution specification number 730 of 1937) (‘foolscap’ is sometimes shortened to ‘’cap’ or ‘cap’)	13Template:SfracTemplate:Pprime × 24Template:SfracTemplate:Pprime (before the 1925 standardisation, 13Template:SfracTemplate:Pprime × 24Template:SfracTemplate:Pprime)
Sheet‑and‑a‑third small foolscap (introduced by the 1925 standardisation) (known as ‘sheet‑and‑a‑third foolscap’ before British Standards Institution specification number 730 of 1937) (‘foolscap’ is sometimes shortened to ‘’cap’ or ‘cap’)	13Template:SfracTemplate:Pprime × 22Template:Pprime
Small demy (known as ‘demy’ before the 1925 standardisation)	15Template:SfracTemplate:Pprime × 20Template:Pprime
Small foolscap (known as ‘foolscap’ before British Standards Institution specification number 730 of 1937) (‘foolscap’ is sometimes shortened to ‘’cap’ or ‘cap’)	13Template:SfracTemplate:Pprime × 16Template:SfracTemplate:Pprime
Small medium (known as ‘medium’ before the 1925 standardisation)	17Template:SfracTemplate:Pprime × 22Template:Pprime
Small post (introduced by the 1925 standardisation)	14Template:SfracTemplate:Pprime × 18Template:SfracTemplate:Pprime
Small royal (known as ‘royal’ before the 1925 standardisation)	19Template:Pprime × 24Template:Pprime
Super royal	19Template:Pprime × 27Template:Pprime (before the 1925 standardisation, 19Template:SfracTemplate:Pprime × 27Template:Pprime)
Printing paper
Copy	16Template:SfracTemplate:Pprime × 20Template:Pprime
Crown	15Template:Pprime × 20Template:Pprime
Demy	17Template:SfracTemplate:Pprime × 22Template:SfracTemplate:Pprime
Double crown	20Template:Pprime × 30Template:Pprime
Double demy	22Template:SfracTemplate:Pprime × 35Template:Pprime
Double elephant (also known as ‘double large royal’) (adopted by British Standards Institution specification number 730 of 1937 but not the 1925 standardisation)	27Template:Pprime × 40Template:Pprime
Double globe	28Template:Pprime × 38Template:Pprime
Double imperial	30Template:Pprime × 44Template:Pprime
Double foolscap (known as ‘double large foolscap’ after the 1925 standardisation and before being re‑named by British Standards Institution specification number 730 of 1937) (‘foolscap’ is sometimes shortened to ‘’cap’ or ‘cap’)	17Template:Pprime × 27Template:Pprime
Double large post	21Template:Pprime × 33Template:Pprime
Double medium	23Template:Pprime × 36Template:Pprime
Double post (adopted by British Standards Institution specification number 730 of 1937 but not the 1925 standardisation)	19Template:Pprime × 30Template:Pprime (prior to re‑definition by British Standards Institution specification number 730 of 1937, 19Template:SfracTemplate:Pprime × 31Template:SfracTemplate:Pprime)
Double pott	15Template:Pprime × 25Template:Pprime
Double royal	25Template:Pprime × 40Template:Pprime
Elephant	23Template:Pprime × 28Template:Pprime
Foolscap (known as ‘large foolscap’ after the 1925 standardisation and before being re‑named by British Standards Institution specification number 730 of 1937) (‘foolscap’ is sometimes shortened to ‘’cap’ or ‘cap’)	13Template:SfracTemplate:Pprime × 17Template:Pprime
Imperial	22Template:Pprime × 30Template:Pprime
Large post	16Template:SfracTemplate:Pprime × 21Template:Pprime
Large royal (introduced by the 1925 standardisation)	20Template:SfracTemplate:Pprime × 27Template:Pprime (prior to re‑definition by British Standards Institution specification number 730 of 1937, 20Template:Pprime × 27Template:Pprime)
Medium	18Template:Pprime × 23Template:Pprime
Music demy	14Template:SfracTemplate:Pprime × 20Template:SfracTemplate:Pprime
Post (adopted by British Standards Institution specification number 730 of 1937 but not the 1925 standardisation)	15Template:Pprime × 19Template:Pprime (prior to re‑definition by British Standards Institution specification number 730 of 1937, 15Template:SfracTemplate:Pprime × 19Template:SfracTemplate:Pprime)
Pott	12Template:SfracTemplate:Pprime × 15Template:Pprime
Quad crown	30Template:Pprime × 40Template:Pprime
Quad demy	35Template:Pprime × 45Template:Pprime
Quad foolscap (known as ‘quad large foolscap’ after the 1925 standardisation and before being re‑named by British Standards Institution specification number 730 of 1937) (‘foolscap’ is sometimes shortened to ‘’cap’ or ‘cap’)	27Template:Pprime × 34Template:Pprime
Quad globe	38Template:Pprime × 56Template:Pprime
Quad pott	25Template:Pprime × 30Template:Pprime
Quad royal	40Template:Pprime × 50Template:Pprime
Royal	20Template:Pprime × 25Template:Pprime
Super royal	20Template:SfracTemplate:Pprime × 27Template:SfracTemplate:Pprime
Wrapping paper
Bag cap	20Template:Pprime × 24Template:Pprime (prior to re‑definition by British Standards Institution specification number 730 of 1937, 19Template:SfracTemplate:Pprime × 24Template:Pprime)
Casing	36Template:Pprime × 46Template:Pprime (across the island of Ireland, 36Template:Pprime × 48Template:Pprime)
Double bag cap*	24Template:Pprime × 39Template:Pprime*
Double crown	20Template:Pprime × 30Template:Pprime
Double double imperial	45Template:Pprime × 58Template:Pprime
Double elephant*	31Template:Pprime × 46Template:Pprime*
Double imperial	29Template:Pprime × 45Template:Pprime
Double medium	23Template:Pprime × 36Template:Pprime
Double small cap*	25Template:Pprime × 34Template:Pprime*
Double small hand*	20Template:Pprime × 29Template:Pprime*
Elephant*	24Template:Pprime × 32Template:Pprime*
Extra large casing	40Template:Pprime × 48Template:Pprime
Haven cap* (sometimes called ‘havon cap’)	21Template:Pprime × 26Template:Pprime*
Imperial	22Template:SfracTemplate:Pprime × 29Template:Pprime
Kent cap*	18Template:Pprime × 21Template:Pprime*
Lumber hand*	17Template:SfracTemplate:Pprime × 22Template:SfracTemplate:Pprime*
Quad crown	30Template:Pprime × 40Template:Pprime
Quad foolscap* (known as ‘quad large foolscap’ after the 1925 standardisation and before British Standards Institution specification number 730 of 1937) (‘foolscap’ is sometimes shortened to ‘’cap’ or ‘cap’)	27Template:Pprime × 34Template:Pprime*
Quad royal*	40Template:Pprime × 50Template:Pprime*
Quad small hand*	30Template:Pprime × 40Template:Pprime*
Royal*	20Template:Pprime × 25Template:Pprime*
Saddleback	36Template:Pprime × 45Template:Pprime
Small cap*	17Template:Pprime × 25Template:Pprime*
Small hand*	15Template:Pprime × 20Template:Pprime*
(No name)	20Template:Pprime × 24Template:Pprime*
(No name)	20Template:Pprime × 28Template:Pprime*
(No name)	21Template:Pprime × 31Template:Pprime*
(No name)	21Template:Pprime × 34Template:Pprime*
(No name)	22Template:Pprime × 32Template:Pprime*
(No name)	22Template:Pprime × 35Template:Pprime*
(No name)	23Template:Pprime × 34Template:Pprime*
(No name)	24Template:Pprime × 30Template:Pprime*
(No name)	24Template:Pprime × 36Template:Pprime*
(No name)	24Template:Pprime × 40Template:Pprime*
(No name)	26Template:Pprime × 36Template:Pprime*
(No name)	28Template:Pprime × 45Template:Pprime*
(No name)	29Template:Pprime × 44Template:Pprime*
(No name)	30Template:Pprime × 38Template:Pprime*
(No name)	30Template:Pprime × 46Template:Pprime*
(No name)	34Template:Pprime × 36Template:Pprime*
(No name)	36Template:Pprime × 36Template:Pprime*
(No name)	36Template:Pprime × 48Template:Pprime*
(No name)	38Template:Pprime × 48Template:Pprime*
(No name)	45Template:Pprime × 56Template:Pprime*

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 ‘[number]lb [paper 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 ‘[number]lb [paper size] [number 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 common 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 Template:Abbr to Template:Abbr), 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 Template:Abbr to Template:Abbr), 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)Template:Efn

To convert between the basis weights of the same paper with different basis‑ream sizes (e. g., from Template:Abbr to Template:Abbr), one may either use the previous formula or the one below:

Weight of the source ream × Applicable conversion factor from the table below

To → From ↓	480	500	504	516
480	…	1·042	1·05	1·075
500	0·96	…	1·01	1·032
504	0·95	0·992	…	1·022
516	0·93	0·969	0·977	…

To convert from a basis weight to its equivalent grammage, the following is the applicable formula:

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:

Table of conversion factors for British units of basis weight (standardised basis sizes and 500‑sheet basis reams only) and their metric and American equivalents

Note 1: Value of Template:Abbr × Relevant conversion factor = Value of the unit in the left column Note 2: Value of a unit in the left column ÷ Relevant conversion factor = Value of Template:Abbr Note 3: To convert between any two units in the left column, Value of the source unit × (Conversion factor for the target unit ÷ Conversion factor for the source unit) Note 4: Note that, as a matter of mathematical relationship, 1 ‘single’ unit (e. g., Template:Abbr) is always equal to 2 ‘double’ unit (e. g., Template:Abbr) and 4 ‘quad’ unit (e. g., Template:Abbr), respectively. By the same token, 1 ‘double’ unit is always equal to Template:Sfrac ‘single’ unit and 2 ‘quad’ unit, respectively; and 1 ‘quad’ unit is always equal to Template:Sfrac ‘double’ unit and Template:Sfrac ‘single’ unit, respectively. Due to the rounding of the conversion factors in this table, calculating with the conversion factors alone may not produce such results automatically.
	Template:AbbrTemplate:Efn (UK)
Template:Abbr (UK)	1·219047
Template:Abbr (the definition on the island of Great Britain) (UK)	4·205713
Template:Abbr (the definition on the island of Ireland) (UK)	4·388570
Template:Abbr (UK)	1·523809
Template:Abbr (UK)	2
Template:Abbr (UK)	6·628570
Template:Abbr (UK)	2·742856
Template:Abbr (UK)	1·165714
Template:Abbr (UK)	3·352380
Template:Abbr (UK)	3·314285
Template:Abbr (UK)	1·759999
Template:Abbr (UK)	2·102856
Template:Abbr (UK)	1·447619
Template:Abbr (UK)	2·539681
Template:Abbr (UK)	1·574603
Template:Abbr (UK)	1·110475
Template:Abbr (UK)	4·876188
Template:Abbr (UK)	0·582857
Template:Abbr (UK)	1·676190
Template:Abbr (UK)	1·657142
Template:Abbr (UK)	0·880000
Template:Abbr (UK)	1·405713
Template:Abbr (UK)	1·051428
Template:Abbr (UK)	0·723809
Template:Abbr (UK)	3·047619
Template:Abbr (UK)	4
Template:Abbr (UK)	2·331429
Template:Abbr (UK)	1·269840
Template:Abbr (UK)	4·114285
Template:Abbr (UK)	0·832857
Template:Abbr (UK)	0·740317
Template:Abbr (UK)	0·787301
Template:Abbr (UK)	0·555237
Template:Abbr (UK)	1·158094
Template:Abbr (metric)	3·571142
Template:Abbr (US)	0·949841
Template:Abbr (US)	1·628571
Template:Abbr (US)	1·320634
Template:Abbr (US)	1·975236
Template:Abbr (US)	2·194284
Template:Abbr (US)	2·412696

Table of conversion factors for British units of basis weight (all basis sizes and basis‑ream sizes) and their metric and American equivalents

Note 1: Value of Template:Abbr × Relevant conversion factor = Value of the unit in the left column Note 2: Value of a unit in the left column ÷ Relevant conversion factor = Value of Template:Abbr Note 3: To convert between any two units in the left column, Value of the source unit × (Conversion factor for the target unit ÷ Conversion factor for the source unit) Note 4: Note that, as a matter of mathematical relationship, as long as the ream size is the same, 1 ‘single’ unit (e. g., Template:Abbr) is always equal to 2 ‘double’ unit (e. g., Template:Abbr) and 4 ‘quad’ unit (e. g., Template:Abbr), respectively. By the same token, 1 ‘double’ unit is always equal to Template:Sfrac ‘single’ unit and 2 ‘quad’ unit, respectively; and 1 ‘quad’ unit is always equal to Template:Sfrac ‘double’ unit and Template:Sfrac ‘single’ unit, respectively. Due to the rounding of the conversion factors in this table, calculating with the conversion factors alone may not produce such results automatically.
	Template:AbbrTemplate:Efn (UK)
Template:Abbr (UK)	2·155275
Template:Abbr (UK)	2·245079
Template:Abbr (UK)	2·263039
Template:Abbr (UK)	2·316921
Template:Abbr (the pre–‍1937 standardisation definition) (UK)	1·141027
Template:Abbr (the pre–‍1937 standardisation definition) (UK)	1·188571
Template:Abbr (the pre–‍1937 standardisation definition) (UK)	1·198079
Template:Abbr (the pre–‍1937 standardisation definition) (UK)	1·226605
Template:Abbr (UK)	1·170285
Template:Abbr (UK)	1·219047
Template:Abbr (UK)	1·228799
Template:Abbr (UK)	1·258056
Template:Abbr (definition on the island of Great Britain) (UK)	4·037483
Template:Abbr (definition on the island of Great Britain) (UK)	4·205713
Template:Abbr (definition on the island of Great Britain) (UK)	4·239357
Template:Abbr (definition on the island of Great Britain) (UK)	4·340294
Template:Abbr (definition on the island of Ireland) (UK)	4·213026
Template:Abbr (definition on the island of Ireland) (UK)	4·388570
Template:Abbr (definition on the island of Ireland) (UK)	4·423677
Template:Abbr (definition on the island of Ireland) (UK)	4·529003
Template:Abbr (UK)	0·804571
Template:Abbr (UK)	0·838095
Template:Abbr (UK)	0·844799
Template:Abbr (UK)	0·864914
Template:Abbr (UK)	0·731428
Template:Abbr (UK)	0·761905
Template:Abbr (UK)	0·768000
Template:Abbr (UK)	0·786285
Template:Abbr (UK)	0·960000
Template:Abbr (UK)	1·008000
Template:Abbr (UK)	1·032000
Template:Abbr (UK)	2·282055
Template:Abbr (UK)	2·377142
Template:Abbr (UK)	2·396159
Template:Abbr (UK)	2·453210
Template:Abbr (UK)	1·462856
Template:Abbr (UK)	1·523809
Template:Abbr (UK)	1·535999
Template:Abbr (UK)	1·572571
Template:Abbr (UK)	1·919999
Template:Abbr (UK)	2
Template:Abbr (UK)	2·015999
Template:Abbr (UK)	2·063999
Template:Abbr (UK)	6·363425
Template:Abbr (UK)	6·628570
Template:Abbr (UK)	6·681596
Template:Abbr (UK)	6·840682
Template:Abbr (UK)	2·633141
Template:Abbr (UK)	2·742856
Template:Abbr (UK)	2·764798
Template:Abbr (UK)	2·830627
Template:Abbr (UK)	3·476721
Template:Abbr (UK)	3·621586
Template:Abbr (UK)	3·650557
Template:Abbr (UK)	3·737475
Template:Abbr (UK)	1·119085
Template:Abbr (UK)	1·165714
Template:Abbr (UK)	1·175040
Template:Abbr (UK)	1·203017
Template:Abbr (UK)	2·594132
Template:Abbr (UK)	2·702221
Template:Abbr (UK)	2·723838
Template:Abbr (UK)	2·788691
Template:Abbr (UK)	3·218284
Template:Abbr (UK)	3·352380
Template:Abbr (UK)	3·379198
Template:Abbr (UK)	3·459655
Template:Abbr (UK)	3·181712
Template:Abbr (UK)	3·314285
Template:Abbr (UK)	3·340798
Template:Abbr (UK)	3·420341
Template:Abbr (UK)	1·689599
Template:Abbr (UK)	1·759999
Template:Abbr (UK)	1·774079
Template:Abbr (UK)	1·816319
Template:Abbr (UK)	2·018741
Template:Abbr (UK)	2·102856
Template:Abbr (UK)	2·119678
Template:Abbr (UK)	2·170147
Template:Abbr (the pre–‍1937 standardisation definition) (UK)	1·412875
Template:Abbr (the pre–‍1937 standardisation definition) (UK)	1·471745
Template:Abbr (the pre–‍1937 standardisation definition) (UK)	1·483518
Template:Abbr (the pre–‍1937 standardisation definition) (UK)	1·518840
Template:Abbr (the pre–‍1937 standardisation definition) (UK)	1·454932
Template:Abbr (the pre–‍1937 standardisation definition) (UK)	1·515555
Template:Abbr (the pre–‍1937 standardisation definition) (UK)	1·527679
Template:Abbr (the pre–‍1937 standardisation definition) (UK)	1·564052
Template:Abbr (UK)	1·389714
Template:Abbr (UK)	1·447619
Template:Abbr (UK)	1·459199
Template:Abbr (UK)	1·493942
Template:Abbr (UK)	0·914285
Template:Abbr (UK)	0·952380
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Template:Abbr (UK)	1·365333
Template:Abbr (UK)	1·422222
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Template:Abbr (UK)	1·666559
Template:Abbr (UK)	1·706239
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Template:Abbr (UK)	1·813333
Template:Abbr (UK)	1·827839
Template:Abbr (UK)	1·871359
Template:Abbr (UK)	1·716418
Template:Abbr (UK)	1·787936
Template:Abbr (UK)	1·802239
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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 17Template:Sfrac or 19Template:SfracTemplate:Abbr (70 or 80gsm); personal and business letter paper, especially that with engraved letterheads, is typically 24Template:Sfrac–29Template:SfracTemplate:Abbr (100–120gsm); greetings cards are usually 85Template:Sfrac–106Template:SfracTemplate:Abbr (200–250gsm); newspaper paper is typically 15–23Template:SfracTemplate:Abbr (35–55gsm); business cards are usually 128–149Template:SfracTemplate:Abbr (300–350gsm); two‑ply toilet rolls and paper kitchen towels are 7Template:SfracTemplate:Abbr (31gsm) (both layers combined) and 17Template:Abbr (40gsm), respectively; and the typical department‑store wrapping paper is commonly 46Template:Sfrac–65Template:Abbr (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 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 = Template:Frac in = 25.4 μm). Commonly, 20-pound bond paper ranges between roughly Template:Cvt in thickness.

The paper density 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 conversions between metres and micrometres (a conversion factor of 1,000,000).Template:Fact

See also

• Density
  • Area density
  • Linear density

• Envelope size
• Hole punch — filing holes
• Index card
• Paper and ink testing
• Photo print sizes

External links

• Understanding Paper Weights
• Understanding paper weight (Staples, Inc.)
• M-weight Calculator
• Paper Weight Calculator
• Paper Weight Conversion GSM to LBS