Inches
Abbreviation/Symbol:
in
" (a double prime)
(For example, six inches can be symbolised as either 6in or 6").
Unit of:
Worldwide use:
The inch is both an imperial unit and part of the US system of customary units and as such the inch has widely been used in the past. The inch is still a common unit in the US, and is popular in Canada and the UK. Japanese manufacturers such as Sony and T
Outside the United States the inch lives on as a size label: car wheel rims are sized in inches everywhere, and pipe sizes such as 1/2-inch are named in inches too.
Screws, bolts and hand tools made in the United States are still sized in inches, and a 1/4-inch bolt is 6.35mm. Screens are sold in inches worldwide, so a 55-inch TV measures 139.7cm across the diagonal.
Definition:
Use of the inch can be traced back as far as the 7th century. The first explicit definition we could find of its length was after 1066 when it was defined as the length of three barleycorns. This was not a satisfactory reference as barleycorn lengths vary naturally. The British Standards Institute defined the inch as 25.4mm in 1930 in the document "Metric Units in Engineering: Going SI". In March 1932 the American Standards Association were asked to rule on whether to adopt the same value (at the time the American inch was 1/.03937 mm which approximated to 25.400051 mm). Because the values were so close, and because Britain has already settled on that value, the ASA adopted this value on March 13, 1933.
The inch is 1/12 of a foot and exactly 2.54cm. Fractions of an inch are made by halving – half-inch, quarter-inch, eighth-inch and so on – rather than by tens, so 3/8 inch comes out at an awkward 9.525mm.
Origin:
The inch has been used as a unit of measurement in the United Kingdom since at least the seventh century, and in 1066 was defined as being equal to the length of three dried barleycorns placed end-to-end (a definition which survived for several centuries).
In 12th-century Scotland the inch was the width of a man's thumb at the base of the nail. Many European languages still use the same word for inch and thumb, such as French pouce and Italian pollice.
The English word inch derives from the Latin uncia, meaning one-twelfth part (an inch traditionally being 1/12 of a foot).
Even in the twentieth century various definitions of the inch were still applied around the world, although these differed by less than 0.001%. In 1930 the British Standards Institution adopted an inch of exactly 25.4mm, with the American Standards Association doing likewise in 1933, and the first country to legally adopt this definition was Canada in 1951.
In 1959 the United States and British Commonwealth countries signed a treaty agreeing to the standardised 25.4mm definition.
The English word inch is derived from the Latin word uncia, which means “one twelfth” – Because an inch was defined as being one twelfth of a foot. The word inch in other languages is often similar to the word ‘thumb’, as thumb width was a measure used to define an inch – for instance King David 1 of Scotland defined the inch as being “the breadth of the thumb of a middle sized man, measured at the root of the nail’ . In England we can find the definition of an inch as the length of 3 barleycorns in a statue of Edward 2nd in 1324.
Common references:
A United States quarter (25 cent) coin is just under one inch in diameter.
A fully-grown human eyeball is roughly one inch in diameter.
1 foot, 12 inches
1 metre, 39.37008 inches
45 RPM vinyl singles – the popular way to buy music from the 1960s to 1990s – Normally had a diameter of 7 inches. Long players (LPs) normally had a diameter of 12 inches
Rulers normally come marked for 30cm and 12 inches, since 12 inches = 30.048 cm
A can of Coke is 4.83 inches high
Usage context:
The inch is both an imperial unit and part of the US system of customary units and as such the inch has widely been used in the past. The inch is still a common unit in the US, and is popular in Canada and the UK. Japanese manufacturers such as Sony and T