Convert between length units
The meter is the SI base unit of length, defined as the distance light travels in 1/299,792,458 of a second. All metric length units (km, cm, mm) are decimal multiples of the meter.
First convert everything to inches (feet × 12 + inches), then multiply by 2.54. For example, 5'6" = 66 inches × 2.54 = 167.64 cm. Or multiply feet by 30.48 and add inches × 2.54.
A nautical mile (1.852 km) is based on Earth's circumference—1 minute of latitude. A statute mile (1.609 km) is the common land mile. Nautical miles are used in aviation and marine navigation.
In 1959, an international agreement standardized the inch as exactly 25.4 mm to simplify conversions. Before this, British and American inches differed slightly, causing confusion in manufacturing.
Hands (4 inches) measure horse height. Fathoms (6 feet) measure water depth. Light-years measure astronomical distances. Points (1/72 inch) and picas measure typography. Each serves its specific domain.
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