Units of Measure

Here we have provided definitions and descriptions of various units of measure that are utilized in the land information services industry.

Acre

The (English) acre is a unit of area equal to 43,560 square feet, or 10 square chains, or 160 square poles. A square mile is 640 acres. The Scottish acre is 1.27 English acres.

Arpent

Unit of length and area used in France, Louisiana and Canada. As a unit of length, an arpent is approximately 191.8 feet. The (square) arpent is a unit of area, approximately .85 acres.

Chain

Unit of length usually understood to be Gunter’s chain (see definition below), but possibly variant by locale. Chains equal to two poles (one half the standard length) are found in Virginia. The name comes from the heavy metal chain of 100 links that was used by surveyors to measure property bounds.

Engineer’s Chain

A 100-foot chain containing 100 links of one foot apiece.

Gunter’s Chain

Unit of length equal to 66 feet, or four poles. This unit was apparently defined as one tenth of a furlong, a common unit of length in the old days. The mile was redefined from 5,000 feet to 5,280 feet in order to be an even multiple of furlongs. A mile is 80 chains.

Hectare

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

Hide

Old English unit of area usually equal to 120 acres.

Labor

The labor is a unit of area used in Mexico and Texas. In Texas it equals 177.14 acres (or one million square varas).

League (legua)

Unit of area used in the southwest U.S., equal to 25 labors, or 4,428 acres (Texas), or 4,439 acres (California).

Link

Unit of length equal to 1/100 chain (7.92 inches).

Perch

See pole.

Pole

Unit of length and area. Also known as a perch or rod. As a unit of length, equal to 16.5 feet. 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.

Rod

See pole.

Rood

Unit of area usually equal to 1/4 acre.

Vara

Unit of length (the “Spanish yard”) used in the southwest. The vara is used throughout the Spanish-speaking world and has values around 33 inches, depending on locale. The legal value in Texas was set to 33 1/3 inches early this century.