The Question:Does an acre have to have a specific shape? In The Wall by Pink Floyd, the teacher says the area of an acre is a rectangle that is one furlong in length and one chain in width. How long is a chain and how wide is a furlong? The Answer:Not as such. The original definition of an acre was, indeed, 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. An ovalshaped 43,560 squarefoot plot will still be 1 acre in size. For more information, and metric equivalents, try our nifty conversion calculator. â€”The Fact Monster 
