In early times the natural way to measure lengths was to use various portions of the body (the foot, the thumb, the forearm, etc.). According to tradition, a yard measured on King Henry I (1068-1135) of England became the standard yard still used today. It was the distance from his nose to the middle fingertip of his extended arm.

Other measures were derived from physical activity such as a pace, a league (distance that equaled an hour's walking), an acre (amount plowed in a day), a furlong (length of a plowed ditch), etc., but obviously these units were unreliable. The ell, based on the distance between the elbow and index fingertip, was used to measure out cloth. It ranged from 0.513 to 2.322 meters depending on the locality where it was used and even on the type of goods measured.

Below are listed some linear measurements that evolved from this old reckoning into U.S. customary measures:

U.S. customary linear measures

1 hand = 4 inches

1 foot = 12 inches

1 yard = 3 feet

1 rod (pole or perch) = 16.5 feet

1 fathom = 6 feet

U.S. customary linear measures

1 furlong = 220 yards or 660 feet or 40 rods

1 (statute) mile = 1,760 yards or 5,280 feet or 8 furlongs

1 league = 5,280 yards or 15,840 feet or 3 miles

1 international nautical mile = 6,076.1 feet

Conversion to metric

1 inch = 2.54 centimeters

1 foot = 0.304 meters

1 yard = 0.9144 meters

1 fathom = 1.83 meters

1 rod = 5.029 meters

1 furlong = 201.168 meters

1 league = 4.828 kilometers

1 mile = 1.609 kilometers

1 international nautical mile = 1.852 kilometers

The Handy Science Answer Book. 2003 ©Visible Ink Press (handyanswers.com). All rights reserved.