Land Area Glossary
Definitions for every unit, term, and system you will encounter in US land measurement, surveying, and real estate.
Updated April 2026
Acre
A unit of area equal to 43,560 square feet (international standard). Defined as one chain (66 ft) by one furlong (660 ft). Used in real estate in the US, UK, Canada, Australia, and India.
More detailsArpent
A historical French colonial land measurement, approximately 191-192 feet in length and about 0.84-0.85 acres for a square arpent. Still referenced in old Louisiana and Quebec land records.
Bigha
A traditional South Asian land unit used in India, Nepal, and Bangladesh. Size varies by region: a pucca bigha in parts of Uttar Pradesh = 1/3 acre; a kutcha bigha = about 1/5 acre. Always confirm the local definition.
Builder's Acre
An informal US term used by home builders, typically about 40,000 sq ft (92% of a standard acre). Not a legal definition. Always confirm the actual square footage when you see this term.
More detailsChain (Gunter's Chain)
A measuring instrument and unit of length of exactly 66 feet (22 yards, 100 links). Developed by Edmund Gunter in 1620. One acre = 10 square chains. 80 chains = 1 mile. The chain is the origin of the 43,560 sq ft acre.
More detailsCommercial Acre
A historical US real-estate convention, typically about 36,000 sq ft (82.6% of a standard acre). Accounts for street, sidewalk, and alley dedications when subdividing. Not a legal or SI unit.
More detailsFurlong
A unit of length equal to 660 feet (220 yards, 1/8 of a mile). Old English for 'furrow long' - the distance an ox team could plow without rest. Together with the chain (66 ft), one furlong x one chain = one acre.
More detailsHectare
A metric unit of area equal to exactly 10,000 square metres (100m x 100m). One hectare = 2.47105 acres. The global standard for agricultural and large land-area measurement outside the Anglophone world.
More detailsHomestead Act (1862)
US federal legislation that granted 160 acres (one quarter-section) of federal land to settlers who farmed it for five years. The act opened 270 million acres of western land to settlement and established the quarter-section as a cultural land reference.
More detailsInternational Foot
Exactly 0.3048 metres. Defined by the 1959 International Yard and Pound Agreement. Used globally for all modern measurements. The US survey foot was deprecated in favour of the international foot on October 1, 2022.
More detailsLink
One hundredth of a Gunter's chain, equal to 7.92 inches (approximately 20.12 cm). One acre = 10 chains x 10 chains = 100,000 square links. The link is now obsolete in practice.
Metes and Bounds
A land survey method describing a parcel by its boundary lines and corners, using compass bearings and distances. Used in the original 13 US states, Texas, and most of Kentucky and Tennessee. Predates and differs from the PLSS grid system.
More detailsPLSS (Public Land Survey System)
The grid-based land survey system used to survey most US land west of Ohio. Created by the Land Ordinance of 1785. Divides land into townships (6x6 miles), sections (1 sq mi, 640 acres), and subdivisions. Administered by the Bureau of Land Management.
More detailsQuarter Section
One quarter of a PLSS section, equal to 160 acres (half-mile x half-mile, 2,640 x 2,640 feet). The classic Homestead Act 1862 grant size. Referenced in deeds as NW 1/4, SW 1/4, NE 1/4, or SE 1/4 of a given section.
More detailsRange
The east-west designation of a township in the PLSS. A range number indicates how many six-mile columns east or west of a principal meridian the township lies. Example: R 7 E = 7th range east of the principal meridian.
More detailsRod (also: Pole or Perch)
A unit of length equal to 16.5 feet (1/4 of a chain, 5.5 yards). Used in pre-metric surveying. One acre = 160 square rods. The rod is now obsolete in most practical surveying.
Section
A PLSS unit equal to 640 acres (1 square mile). A township contains 36 sections, numbered 1-36 in a boustrophedon (back-and-forth) pattern starting from the northeast corner of the township.
More detailsSquare Mile
A unit of area equal to exactly 640 acres, or 27,878,400 square feet. Under the PLSS, a square mile = one section. Used in the US for large geographic areas and federal land statistics.
More detailsTownship
A PLSS unit of land measuring 6 miles by 6 miles (36 square miles = 23,040 acres). Each township is identified by a north-south township number and east-west range number relative to a principal meridian. Contains 36 one-square-mile sections.
More detailsUS Survey Foot (deprecated)
A unit of length equal to 1200/3937 metres (approximately 0.30480060960 m), used in US federal land surveys from 1893 to October 1, 2022. Slightly longer than the international foot (0.3048 m). Deprecated by the NGS on October 1, 2022.
More details