The
acre is a
unit of
area in a
number of different systems, including the
imperial and
U.S. customary
systems. The most commonly used acres today are the international
acre and, in the United States, the survey acre.
One international acre is equal to 4,046.8564224
m^{2}. One U.S. survey acre is equal
to m
^{2} = 4,046.8726098 m
^{2}.
The area of one acre (red) overlaid on
an American football field
One acre comprises 4,840
square yards or
43,560
square feet (which can be easily
remembered as 44,000 square feet, less 1%; or as the product of 66
x 660). Because of alternative definitions of a yard or a foot, the
exact size of an acre also varies slightly. Originally, an acre was
understood as a
selion of land sized at one
furlong (660 ft) long and one
chain (66 ft) wide; this may have also
been understood as an approximation of the amount of land an
ox could plow in one day. A
square enclosing one acre is approximately
208 feet and 9 inches (63.6 meters) on a side. But as a unit
of measure an acre has no prescribed configuration; any perimeter
enclosing 43,560 ft
^{2} is an acre in size.
The acre is often used to express areas of land. In the
metric system, the
hectare is commonly used for the same purpose. An
acre is approximately 40% of a hectare.
One acre is 90.75 percent of a 53.33-yard-wide
American football field. The full field,
including the end zones, covers approximately .
International acre
In 1958,
the United
States and countries of the Commonwealth of Nations defined the
length of the international yard to be 0.9144
meters. Consequently, the international
acre is exactly 4,046.8564224
square
meters.
United States survey acre
The United States survey acre is approximately 4,046.873
square meters; its exact value ( m²) is based
on an inch defined by 1 meter = 39.37 inches exactly, as
established by the
Mendenhall
Order.
Equivalence to other units of area
1 international acre is equal to the following metric units:
- 4,046.8564224 square meters
- 0.40468564224 hectare (A square with 100
m sides has an area of 1 hectare.)
1 United States survey acre is equal to:
1 acre (both variants) is equal to the following customary
units:
- 66 feet × 660 feet (43,560 square
feet)
- 1 chain × 10 chains (1 chain = 66 feet = 22 yards = 4 rods =
100 links)
- 1 acre is approximately 208.71 feet × 208.71 feet (a
square)
- 4,840 square yards
- 160 perches. A perch is equal to a
square rod (1 square rod is
0.00625 acre)
- 10 square chain
- 4 roods
- A chain by a furlong (chain 22 yards, furlong 220 yards)
- 1/640 (0.0015625) square mile (1
square mile is equal to 640 acres)
1 international acre is equal to the following Indian unit:
Historical origin
The word "acre" is derived from
Old
English æcer (originally meaning "open field",
cognate to west coast Norwegian language
"ækre" and
Swedish "åker",
German Acker,
Latin ager and
Greek αγρος (
agros).
The acre was approximately the amount of land tillable by one man
behind an
ox in one
day. This
explains one definition as the area of a rectangle with sides of
length one
chain and one
furlong. A long narrow strip of land is more
efficient to plough than a square plot, since the plough does not
have to be turned so often. The word "furlong" itself derives from
the fact that it is
one furrow
long.
Before the enactment of the
metric
system, many countries in Europe used their own official acres.
These were
differently sized in different countries, for instance, the
historical French acre was 4,221 square metres, whereas in Germany as many
variants of "acre" existed as there were German
states.
Statutory values for the acre were enacted in England by acts of:
Historically, the size of farms and landed estates in the United
Kingdom was usually expressed in acres (or acres,
roods, and
perches), even
if the number of acres was so large that it might conveniently have
been expressed in square miles. For example, a certain landowner
might have been said to own 32,000 acres of land, not 50 square
miles of land.
Customary acre
The customary acre was a measure of roughly similar size to the
acre described above, but it was subject to considerable local
variation similar to the variation found in
carucates,
virgates,
bovates, nooks, and farundells. However,
there were more ancient measures that were also farthingales. These
may have been multiples of the customary acre, rather than the
statute acre.
Other acres
See also
References
- National Institute of Standards and Technology General Tables of Units of Measurement
- National Bureau of Standards. Refinement of Values for the Yard and the
Pound.
- [1] The Collaborative International Dictionary
of English
External links