An *acre* is a unit of area that historically has been used to measure tracts of land. 1 acre of land is approximately equal to **43,560 sq. ft. **So, if the plot of land is a perfect square, then one side of that square would have a length of ≈**208.71 feet**. If the plot of land is rectangular, we would need to know the length of one side in feet in order to figure out the length of the other, or we would need to know the ratio of the lengths between the two sides.

An acre is a statutory unit of measurement used for legal purposes in the U.S., and used to be a statutory unit of measurement in a number of English-speaking countries and former British colonies. In countries where the acre is not a legal unit of measurement, the acre is still used in informal purpose, though it may have a slightly different definition depending on the region of use. In the U.S., an NFL regulation football field is about 56,000 sq. ft. So, one football field is approximately equal to 1.32 acres. For those in non-US countries, an Association Football regulation pitch is about 1.72 acres.

in terms of miles, 1 acre is about equal to 1/640th of a square mile (0.0015625 sq. mi.). The international symbol for the acre is **ac.**

## Uses Of Acres

Traditionally, the acre has been used as a unit of measurement for land and property, particularly agricultural land. In countries where the acre is used as a unit of measurement, residential and agricultural areas are normally expressed in terms of acres.

In countries like the US where the acre is a statutory unit of measurement, legal documents and legal transactions surrounding ownership and purchasing of land are couched in terms of acres. Most countries that use the acre as a statutory unit of measurement are former British colonies, who inherited the use from their English-speaking colonizers.

In the UK, the acre was an official unit of trade, until 1995, when it was replaced with the hectare, an SI unit equivalent to 10,000 square meters. The acre still remains a common unit of measurement for informal purposes in the UK., including sectors of the agricultural and property industries.

## History Of The Acre

Traditionally, 1 acre was conceived to be equal to the amount of land a single ox could till in one day. The origin of the term acre in agricultural purposes explains its customary use and a unit of land and property. One of the oldest explicit references to an acre as a unit of land measurement comes from an English statutory legal text from the 13th century that defines one acre as a unit of land “40 perches in length and 4 in breadth.” One perch is defined as exactly 16 1/2 feet, so according to this text, one acre is equivalent to (16.5×40)×(16.5×4)= 660×66 = 43,500 sq. ft. The definition of an acre is not based on the shape of the land, i.e. whether it is a square or rectangle. Any tract of land with a square footage of 43,500 is one acre of land, no matter the shape.

Alternatively, one definition of the acre defines 1 acre as the area of a rectangle of land with sides one chain and one furlong in length. One chain is equal to 66 feet (and so 4 perches), and one furlong is 660 feet (and so 40 perches) which is also equal to 10 chains. Thus, the area in square feet of a plot of land one chain by one furlong is 66×660 = 43,560 square feet.

By now a reader might be asking: what is the deal with all these weird units of measurement? As it turns out, most of these “strange” units of measurement like chains or furlongs, are directly based on practical constraints facing farmers in the past. As stated previously, an acre was originally conceived as the total amount of land tillable by a single ox, a common beast of burden that many farmers at the time relied on. The ubiquity of oxen plows in the medieval world made it so a single understanding of an acre as a unit of land tillable by one ox had direct physical significance and practical import. Likewise, the term “furlong” was understood as the length of on furrow along the length of a rectangular acre plot of land.

## Other Units Of Measurement Related To Land And Property

The acre unit and most of the units associated with the acre stem directly from English units that were first standardized by King Henry VIII during the 16th century and later rulers in the 17th century. After Henry VIII broke from the Catholic church and declared himself head of the Anglican Church of England, he began seizing previous Catholic church owned lands. At the time, most principalities in England had their own independent unit systems, and there was no standard to quantify the total amount of land seized Henry VIII introduced several standardized units of land measurement as a means to quantify and easily divide up seized church lands into square and rectangular parcels to sell.

**Rod**

The rod as a unit of measurement is exactly equal to the perch, so 16.5 feet. The original definition of the rod was based on the length of the iron rods used by surveyors to measure land in 16th century England. The rod tool consisted of a stiff iron bar wrapped with a wax-coated cord that was knotted at regular intervals. One square rod is the square measure of a tract of land 1 rod by 1 rod and is equal to 272.5 sq. ft. Additionally, 40 square rods is defined as 1 “rood” and there are 160 square rods (4 roods) to a 1 acre.

Nowadays, the rod does not see much use, except in certain specialized industries. For instance, oil pipeline easements are often couched in terms of “price-per-rods” and recreation canoeing maps measure canoe portages (areas of the trail where a canoe must be carried between bodies of water) in terms of rods. Canoes themselves are often measured in terms of rods as well.

**Chain**

Like the rod, the chain as a unit of measurement was originally based on the lengths of the chains used by English surveyors in the 16th century. 1 chain is equal to 66 feet (4 rods), and one link is 1/100th of a chain, so about 7.92 inches. The official designation of a chain as 66 feet was given by Edmund Gunter, a polymath employed under Queen Elizabeth I in 1620. By 1675, the chain had become the common unit of measurement of length, along with the furlong. Most definitions of the acre are given in terms of chains, where 1 acre is the area of a rectangle with side length of 1 chain and 1 furlong.

The chain made its way into the US via British colonies and was used under the Articles of Confederation as a standard measure of land. In the present day, like many of these other measurements, the chain has been phased out of official usage but retains some us in specialized industries. For instance, many railway companies in the US measure lengths of railroad tracks in terms of “chainage” (analogous to mileage). Similar measurement guided the construction of railroads in the US during the 19th century.

**Furlong**

A furlong is a measure of distance equivalent to one-eighth of a mile, 660 feet, or 40 rods. In SI units, 1 furlong is about 201.168 meters. The name “furlong” comes from the Old English words “furh” and “lang” and was conceived as the vertical length of the furrow in one acre of land. One furlong has also been considered the total distance a team of oxen could plow without stopping for rest. The furlong shows up in older definitions of the acre, as one acre was originally defined as the area of a tract of land 1 furlong by 1 chain (4 rods)

Historically, the furlong has been considered equal to the ancient Greek unit the “stade” which was based on the length of a typical sports stadium at the time. Nowadays, most countries have phased the furlong out of official use, except in a few specialized areas, such as horse racing in English-speaking countries. A notable exception is the country of Myanmar, whose government uses the furlong (as well as the mile) to indicate distances on road and highway signs.

In the US, furlongs show up in historical measurements of residential areas. Chicago’s street numbering system is based on an 8 block per mile housing arrangement, essentially making every block in a typical Chicago neighborhood 1 furlong in length. A similar grid-like arrangement and numbering system is used in Salt Lake City, Utah, and in parts of Phoenix, Arizona.

To sum up, 1 acre is a unit of square area that is defined as the area of land enclosed by a 1 chain by 1-furlong rectangle. 1 acre is equal to 43,560 square feet, and an acre that is a square has a side length of 208.71 feet. The acre is part of a grouping of land measurements that stem from legal statutes enacted in 16th and 17th century England, and many countries still use the acre for purposes of buying, selling, and building on land.