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Length; system unit code (other) symbol or abbrev. notes conversion factor/m combinations SI: gigametre: Gm Gm US spelling: gigameter: 1.0 Gm (620,000 mi) megametre: Mm Mm US spelling: megameter: 1.0 Mm (620 mi) kilometre: km km US spelling: kilometer: 1.0 km (0.62 mi) km mi; hectometre: hm hm US spelling: hectometer: 1.0 hm (330 ft) decametre ...
For measuring length, the U.S. customary system uses the inch, foot, yard, and mile, which are the only four customary length measurements in everyday use. From 1893, the foot was legally defined as exactly 1200 ⁄ 3937 m (approximately 0.304 8006 m). [13] Since July 1, 1959, the units of length have been defined on the basis of 1 yd = 0.9144 ...
Before the establishment of the decimal metric system in France during the French Revolution in the late 18th century, [4] many units of length were based on parts of the human body. [5] [6] The Nippur cubit was one of the oldest known units of length. The oldest known metal standard for length corresponds to this Sumerian unit and dates from ...
Conversions between units in the metric system are defined by their prefixes (for example, 1 kilogram = 1000 grams, 1 milligram = 0.001 grams) and are thus not listed in this article. Exceptions are made if the unit is commonly known by another name (for example, 1 micron = 10 −6 metre).
The other units of length and mass, and all units of area, volume, and derived units such as density were derived from these two base units. Mesures usuelles ( French for customary measures ) were a system of measurement introduced as a compromise between the metric system and traditional measurements.
A unit derived from the base units is used for expressing quantities of dimensions that can be derived from the base dimensions of the system—e.g., the square metre is the derived unit for area, which is derived from length. These derived units are coherent, which means that they involve only products of powers of the base units, without any ...
Wine was measured with units based on the wine gallon of 231 cubic inches (3.785 L), beer was measured with units based on an ale gallon of 282 cubic inches (4.621 L) and grain was measured with the Winchester measure with a gallon of approximately 268.8 cubic inches (one eighth of a Winchester bushel or 4.405 L). In 1824, these units were ...
The conversion between different SI units for one and the same physical quantity is always through a power of ten. This is why the SI (and metric systems more generally) are called decimal systems of measurement units. [10] The grouping formed by a prefix symbol attached to a unit symbol (e.g. ' km ', ' cm ') constitutes a new inseparable unit ...