An acre is a unit for measuring the area in the United States customary units. 1 acre = 208.7 times 208.7 = 43560 ft2
If 1 acre measures the area of a square, each side of the square will have a length of approximately 208.7 feet as shown in the image
1 acre is also equal to 1/640 of a square mile.
In other words, 640 acres = 1 mi2
An acre is about 75% the size of a football field and about 60% of a soccer field.
It is noteworthy to mention that originally 1 acre was the amount of land a farmer using a pair of oxen could plow in 1 day.