D. L. Smith Surveyors

Units of Measure

Acre – The (English) acre is a unit of area equal to 43560 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, 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, but possibly variant by locale. Chains equal to 2 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 4 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 5000 feet to 5280 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 1 million square varas).

League (legua) – Unit of area used in the southwest U.S., equal to 25 labors, or 4428 acres (Texas), or 4439 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.

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.