# Units of Measure

Listed below are the units of measure that surveyor’s use and what they mean. Need help? Give us a call at 757-345-2866.

Acre: A unit of area equal to 43,560 square feet, 10 square chains, or 160 square poles. A square mile is 640 acres.

Chain: Unit of length usually understood to be Gunter’s chain, but could vary by locale. See also Rathbone’s chain. The name comes from the heavy metal chain of 100 links that surveyors used to measure property bounds.

Engineer’s Chain: A 100-foot chain containing 100 links each of which is 1-foot long.

Furlong: Unit of length equal to 40 poles (220 yards). Its name derives from “furrow long”, the length of a furrow that oxen can plow before they are rested and turned. See Gunter’s chain.

Gunter’s chain: Unit of length equal to 66 feet or 4 poles. Developed by English polymath Edmund Gunter in the early 1600s. The standard measuring chain revolutionized surveying. Gunter’s chain was 22 yards long or 1/10 of a furlong, a common unit of length in the old days. An area 1 chain wide by 10 chains long was exactly one acre. In 1595 Queen Elizabeth I had the mile redefined from the old Roman value of 5,000 feet to 5,280 feet in order for it to be an even number of furlongs. A mile is 80 chains.

Hectare: Metric unit of area equal to 10,000 square meters or 2.471 acres.

League: A unit of length that is approximately 3 miles.

Link: A unit of length equal to 1/100 chain (7.92 inches).

Out: An “out” was 10 chains. When counting out long lines, chain carriers would put a stake at the end of a chain, move the chain and put another stake at the end, and so on until they ran “out” of ten stakes.

Perch: See Pole.

Point: A point of the compass. There are four cardinal points (north, south, east, west), and 28 others yielding 32 points of 11.25 degrees each. A survey line's direction could be described as a compass point, as in “NNE” (North Northeast). To improve precision, the points would be further subdivided into halves or quarters as needed.

Pole: Unit of length and area also known as a perch or rod. As a unit of length, one pole equals 16.5 feet. A mile is 320 poles. As a unit of area, equal to a square with sides one pole long, an acre is 160 square poles. It was common to see an area referred to as "87 acres, 112 poles", meaning 87 and 112/160 acres.

Rathbone’s chain: A measuring chain two poles, or 33 feet, in length.

Rod: See Pole.

Rood: Unit of area usually equal to 1/4 acre.