Centimeters
Abbreviation/Symbol:
cm
Unit of:
Worldwide use:
The centimetre is used worldwide as a measurement of length. There are a few exceptions, most notably the United States, which still primarily uses the U.S. Customary (similar to imperial) system.
Definition:
The centimetre is a unit of length in the metric system, equal to one-hundredth of a metre.
1cm is equivalent to 0.39370 inches.
Origin:
The metric, or decimal, system of weights and measures was defined and adopted in France in 1795. Using the metre as the basis for length measurements, the system is now used officially across the globe.
John Wilkins was the first person to publicly recognise the need for a universal length measurement, ie a measurement that could be carried out locally to avoid having to have a definition that refereed to a stored reference unit. He proposed using the length of a “seconds pendulum”. - a pendulum that made half an oscillation per second – as he believed this would have a fixed length. It was later found there is a slight difference in this length around the world. Because of this, the Academy of Sciences devised a new measure, 1/10000000 of the distance from the Equator to the North Pole (measured through Paris). This new value was used to create a metal bar stored at the BIPM’s headquarters known as the “international prototype meter”. This standard has since been superseded by more accurate measures –first by the 11th conference of weights and measures, who defined the meter as “1,650763.73 wavelengths of the orange-red emission line of a krypton-86 atom in a vacuum”. Most recently, in 1983, the 17th conference defined the meter as “the distance travelled by light in a vacuum in 1/299792458 of a second”. From this we derive the centimetre as the distance travelled by light in a vacuum in 1/2997924580 of a second.
Defined at the 17th Conférence Générale des Poids et Mesures (CGPM)
The centimeter dates from the French Revolution, when the Academy of Sciences devised the metric system in 1791.
The meter was first defined as one ten-millionth of the distance from the North Pole to the equator through Paris, and the centimeter as a hundredth of a meter. Everyday small lengths needed something shorter than a meter, and the centimeter spread wherever the metric system did.
Common references:
A United States nickel (5 cent) coin is approximately 2cm diameter.
The cornea of a human eye is approximately 1.15cm (11.5mm) diameter.
One imperial foot is equal to approximately 30.5cm.
1 inch, 2.54 cm
1 metre, 100 cm
30 cm is approximately equal to 1 foot (actually 11.81 inches)
A standard number 2 pencil is 19cm long when new
An average mug from Ikea is about 10cm tall
Theaveragebody.com reports that the palm of an average male is 8.4cm wide and an average female hand is 7.4cm wide
Usage context:
The centimetre is used worldwide as a measurement of length. There are a few exceptions, most notably the United States, which still primarily uses the U.S. Customary (similar to imperial) system.
Body height, clothing measurements and furniture sizes are all given in centimeters almost everywhere outside the US. To convert from inches multiply by 2.54, so a 30 inch waist is 76.2 centimeters.
Laboratory work uses centimeters for apparatus and larger specimens – a standard petri dish is 9 centimeters across – while anything smaller moves to millimeters and micrometers.
Fabric outside the US is sold by the meter, and widths are quoted in centimeters – 140 to 150 centimeters is common for dress fabric.