Length Converter
Convert seamlessly between metric (meters, kilometers, centimeters, millimeters) and imperial or US customary units (feet, inches, yards, miles, nautical miles). All conversions adhere to the international yard and pound agreement where 1 inch is defined as exactly 25.4 mm.
The meter is the SI base unit of length. Originally defined in 1793 as one ten-millionth of the distance from the equator to the North Pole, it is currently defined by the BIPM as the length of the path traveled by light in a vacuum in a time interval of exactly 1 / 299,792,458 of a second.
Prior to July 1, 1959, the United States and the British Commonwealth maintained slightly divergent definitions of the inch. The International Yard and Pound Agreement harmonized the definition so that 1 yard = 0.9144 meters, making 1 inch precisely 25.4 millimeters.