How Big is an Acre?

Updated October 11, 2021 | Infoplease Staff

What is the size of an acre?

The acre was originally an English unit of measurement that described the area of land that a yoke of oxen could plow in a day. It originally differed in size from one area to the next. In the 1900s it was fixed at 4,840 square yards (or 4,047 square meters). It is still used today to describe plots of land. Because an acre is a unit of area, rather than length, it would be incorrect to say "square acre" the way one might say "square mile".

In comparison to other traditional measurements, there are two and a half acres in a hectare. Or, in terms of miles, there are 640 acres in a square mile.

Does it have to be a rectangle?

The original definition of an acre was a furlong by a chain, a definition used by surveyors to measure plots. However, the area one derives from that measurement is an acre, even if it's contained within a different shape. 1 furlong is equal to 10 chains, or 660 feet. If you do the math, this means an acre is 10 square chains, or 43,560 square feet.

Because an acre is a unitof area, not length, it is defined in square feet. An acre plot can be of any shape-a rectangle, a triangle, a circle, or even a star-so long as its area is exactly 43,560 square feet.

To find the linear measurements of other rectangular acres, just divide 43,560 by the number of feet you want on one side. A square-shaped acre would then be about 208.7 by 208.7 feet (because 208.7 x 208.7 = ~43,560). An acre 100 feet wide would be 435.6 feet long (100 x 435.6 = 43,560) and an acre 1 foot wide would be 43,560 feet long.

How many acres is a football field?

An acre of land is often compared to a football field (that is to say, an American football field, not a football pitch). In reality, an acre equals about 76% of a football field, when you consider both end zones.

An NFL football field (including the two end zones) is 360 feet long and 160 feet wide for a total of 57,600 square feet. When you take away the two 30-foot-long end zones at each end, the field is 48,000 square feet, making an acre about 91% of the field.

If you are interested in more information check out our table of Standard Measurements in Sports.