|CONVERT IT!||Traditional Units||Imperial Units|
|Nautical Units||Metric System|
In all traditional measuring systems, short distance units are based on the dimensions of the human body. The inch represents the width of a thumb. The foot (12 inches) was originally the length of a human foot. The yard (3 feet) seems to have gotten its start in England as the name of a 3-foot measuring stick, but it is also understood to be the distance from the tip of the nose to the end of the middle finger of the outstretched hand. Historically, there are many other "natural units" of the same kind, including the palm (width of the palm, 3 inches), the hand (4 inches), the span (width of the outstretched hand, from the tip of the thumb to the tip of the little finger, 9 inches), and the cubit (length of the forearm, 18 inches).
In Anglo-Saxon England (before the Norman conquest of 1066), short distances seem to have been measured in several ways. The inch was defined to be the length of 3 barleycorns, which is very close to its modern length. The shaftment was frequently used, but it was roughly 6.5 inches long. Several foot units were in use, including a foot equal to 12 inches, a foot equal to 2 shaftments (13 inches), and the "natural foot" (pes naturalis, an actual foot length, about 9.8 inches).
When the Normans arrived, they brought back to England the Roman tradition of a 12-inch foot. During the reign of Henry I (1100-1135) the 12-inch foot became official, and the royal government took steps to make this foot length known. A 12-inch foot was inscribed on the base of a column of St. Paul's Church in London, and measurements in this unit were said to be "by the foot of St. Paul's" (de pedibus Sancti Pauli). Henry I also appears to have ordered construction of 3-foot standards, which were called "yards," thus establishing that unit for the first time in England.
Longer distances in England are traditionally measured in miles. The mile is a Roman unit, originally defined to be the length of 1000 paces of a Roman legion. A "pace" here means two steps, right and left, or about 5 feet, so the mile is a unit of roughly 5000 feet. For a long time no one felt any need to be precise about this, because distances longer than a furlong did not need to be measured exactly. It just didn't make much difference whether the next town was 21 or 22 miles away.
In medieval England, various mile units seem to have been used. Eventually, what made the most sense to people was that a mile should equal 8 furlongs, since the furlong was an English unit roughly equivalent to the Roman stadium and the Romans had set their mile equal to 8 stadia. In 1592, Parliament settled this question by setting the length of the mile at 8 furlongs, which works out to 1760 yards or 5280 feet.
Meanwhile, all land in England was traditionally measured by the or rod, an old Saxon unit probably equal to 20 "natural feet." The Norman kings had no interest in changing the length of the rod, since the accuracy of deeds and other land records depended on that unit. Accordingly, the length of the rod was fixed at 5.5 yards (16.5 feet). This was not very convenient, but 5.5 yards happened to be the length of the rod as measured by the 12-inch foot, so nothing could be done about it. In the Saxon land-measuring system, 40 rods make a furlong , the length of the traditional furrow as ploughed by ox teams on Saxon farms. These ancient Saxon units, the rod and the furlong, have come down to us today with essentially no change.
|Inch (in or ")||25.4 millimetres|
|Link 0.66' or 7.92"||201.2 millimetres|
|Foot (ft or ') = 12"||304.8 millimetres|
|Yard (yd) = 3'||914.4 millimetres|
|Rod (rd) = 5.5yds||5.0292 metres|
|Chain (ch) = 22yds = 100links||20.1168 metres|
|Furlong (fur) = 10ch = 40rods = 220yds||201.168 metres|
|Mile (mi) = 8fur = 1760yds = 5280'||1609.344 metres|
The Nautical Mile was originally defined by the admiralty as being 6080 feet it was subdivided into 10 cables each of 608 feet. Another nautical unit was the fathom used as a measure of depth equal to 6 feet.
In 1929 the Nautical Mile was redefined to 1853.184 metres and is still in use for ships and aircraft at the start of 21st century.
1 Nautical Mile = 1.1515 miles = 1853.184 metres = 1.853 kilometres
1 Fathom = 6 feet = 1.828 metres
The base unit of the SI system for length is the metre (m) equal to about about 1.09 yards. The prefix kilo means x 1,000 : 1km = 1,000m. For smaller lengths the meter can be prefixed by milli - 1/1,000 (m) or micro - 1/1,000,000 (µ). It should be noted that centimetres (cm) are still in frequent use in Britain and this unit is a throw back from the old CGS metric system. 1cm is equal to 10 millimetres or 1/100th of a metre.
|1 kilometre (km)||1000 metres (m)||0.621 miles (mi)|
|1 metre (m)||1000 millimetres (mm)||1.093 yards (yd)|
|1mm||0.039 inches (in)|
The controls below will convert the various units to and from metric. Enter a value in one of the boxes click outside the box and the remaining boxes in the row will show the results