Preferred metric sizes


Preferred metric sizes are a set of international standards and de facto standards that are designed to make using the metric system easier and simpler, especially in engineering and construction practices. One of the methods used to arrive at these preferred sizes is the use of preferred numbers and convenient numbers, such as the Renard series and 1-2-5 series, to limit the number of different sizes of components needed.
One of the largest benefits of such limits is an ensuing multiplicative or exponential reduction in the number of parts, tools and other items needed to support the installation and maintenance of the items built using these techniques. This occurs because eliminating one diameter fastener will typically allow the elimination of a large number of variations on that diameter.

Food and beverages

Liquor bottle sizes

International agreements, including 75/106/EEC, specify the capacities of liquor bottles allowed in international commerce as the following 10 sizes:
  • 100 ml
  • 250 ml
  • 375 ml
  • 500 ml
  • 750 ml
  • 1 L
  • 1.5 L
  • 2 L
  • 3 L
  • 5 L
In the United States, the alcohol industry switched to metric bottle sizes on October 1, 1976, abandoning the existing 38 sizes of bottles and instead adopting the following 6 sizes:
  • 50 mL
  • 200 mL
  • 500 mL
  • 750 mL
  • 1000 mL
  • 1750 mL

Building construction

System 32 furniture

System 32 is a standard for the design and manufacture of furniture, most commonly used in the design of cabinets, wherein the major parts are available in increments of 32 mm, and shelf supports consist of columns of 5 mm holes on 32 mm centers.

ISO 2848 basic module

The ISO 2848 basic module is a unit of 100 mm, often represented by a single capital "M", along with 300 mm and 600 mm groupings, that is widely used for the widths of furniture in Europe.
  • A standard metric block is 190 mm wide, 390 mm long, and 190 mm high, which allows for 10 mm mortar joints in between bricks, giving a standard unit size of 200 mm square by 400 mm long.
  • A standard metric brick is 90 by 57 by 190 mm; with 10 mm of mortar, that produces a standard unit of 100 mm x 200 mm.

Office equipment and supplies

ISO 216 paper sizes

ISO 216 standard specifies the A sizes of paper, including the very common A4, wherein the base size of A0 is one square meter, and the ratio between the height and width is, which results in all sizes of paper having the same aspect ratio.
Also related is the set of pen thicknesses for technical drawings.

Manufacturing

ISO 261 and 262 fastener diameters

ISO 261 defines a set of preferred metric machine screw/bolt sizes, and ISO 262 defines a subset of those; both are based roughly on Renard series as defined in ISO 3, ISO 17, and ISO 497. Given that even ISO 262 specifies a fairly large set of diameters, a much simplified set of preferred diameters was developed by one of the lead designers of ASME Z17.1 and ANSI B4.2, Knut O. Kverneland, to reduce the list to 6 preferred sizes, and another 6 intermediate supplementary sizes.
For each size bolt or screw and type of head, there is a corresponding size driver prescribed by various ISO standards, including:
  • Internal hex drive: ISO 2936:2014 "Assembly tools for screws and nuts—Hexagon socket screw keys"
  • External hex drive: ISO 4014, 4016, 4017, and 4018
ISO 262 sizesInternal hex
cap head		Internal hex
button head		Internal hex
flat head screws		Internal hex
set screws		External hex
ISO standard		External hex
DIN standard
M2.52.02.055
M32.52.02.02.05.55.5
M43.02.52.52.577
M54.03.03.03.088
M65.04.04.03.51010
M86.05.05.05.01313
M108.06.06.06.01617
M1210.08.08.08.01819
M1614.010.010.010.02424
M2017.012.012.03030
M2419.03636
M3022.04646

For Torx bolts, there is a corresponding size driver prescribed by Acument, the designer of the Torx drive system., there are no ISO standards for hexalobular drive sizes.
ISO 262 sizesPan headFlat headSocket headSocket ButtonTrussExternal Torx
M2.5T8T8T8
M3T10T10T10T8E4
M4T20T20T25T15T15E5
M5T25T25T27T25T20E6
M6T30T30T30T27T30E8
M8T40T40T45T40T40E10
M10T50T50T50T45T50E12
M12T55T55T55E14
M16T70T60E20
M20T90E24
M24T100E32
M30E36

Similarly, for Torx Plus bolts, there is a corresponding size driver prescribed by Acument, the designer of the Torx Plus drive system., there are no ISO standards for hexalobular drive sizes.
ISO 262 sizesPan headFlat headSocket headSocket ButtonTrussExternal Torx
M2.58IP8IP8IP4EP
M310IP10IP10IP8IP5EP
M420IP15IP20IP15IP15IP7EP
M525IP20IP27IP25IP20IP8EP
M630IP27IP30IP27IP30IP10EP
M845IP30IP45IP40IP40IP14EP
M1050IP50IP50IP45IP50IP16EP
M1255IP55IP55IP55IP55IP20EP
M1670IP60IP26EP
M2090IP32EP
M24100IP40EP
M30

ISO 1307 plastic hose sizes

See also:
  • [|ISO 6708 Nominal Diameter]
ISO 1307:2006, Rubber and plastics hoses—Hose sizes, minimum and maximum inside diameters, and tolerances on cut-to-length hoses specifies nominal diameters for four different types of plastic hoses, including "Type C", which includes the typical garden hose. Each nominal diameter specifies different ID minimum and maximum values. The nominal size is a Renard series.

ISO 6708 nominal pipe diameter

Nominal diameter, abbreviated DN, is the designation system specified by ISO 6708 for specifying the diameter of trade sizes of metric pipework components, and is the metric equivalent to Nominal Pipe Size. It is among several ISO specifications that formalize preferred numbers, and is referred to by numerous other international standards, including ISO 7598 and EN 10255. The complete set of DN values allowed by the standard are:
DN designationDN designationDN designation
DN 10DN 250DN 1 500
DN 15DN 300DN 1 600
DN 20DN 350DN 1 800
DN 25DN 400DN 2 000
DN 32DN 450DN 2 200
DN 40DN 500DN 2 400
DN 50DN 600DN 2 600
DN 60DN 700DN 2 800
DN 65DN 800DN 3000
DN 80DN 900DN 3200
DN 100DN 1 000DN 3 400
DN 125DN 1 100DN 3 600
DN 150DN 1 200DN 3 800
DN 200DN 1 400DN 4 000

The number following the DN is a nominal value that is roughly the number of millimeters of a circular feature on the connection point of the pipe, fitting, coupling, etc., but often differing by a noticeable amount. If the DN value is related to the internal bore diameter of the feature, the size should be represented by DN/ID, and if the DN value is related to the outside diameter, the size should be represented by DN/OD.
The relationship between DN and NPS pipe sizes are as follows. Note that the actual internal diameter varies depending on the pipe wall thickness.
DNActual ODNPS
designationmmdesignation
DN 1017.2
DN 1521.3
DN 2026.9
DN 2533.71
DN 3242.4
DN 4048.3
DN 5060.32
DN 6576.1
DN 8088.93
DN 100114.34
DN 125139.7-
DN 150168.36
DN 200219.18
DN 25027310
DN 300323.912
DN 350355.614
DN 400406.416
DN 45045718
DN 50050820
DN 60061024
DN 70071128
DN 75076232
DN 80081334
DN 90091436
DN 1 000101640
DN 1 200122048