How to Calculate an Acre

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Things You'll Need

  • Measuring wheel
  • Survey flags

Farms, rural properties and large residential lots list and sell by the acre. An acre is a unit of land measurement representing 43,560 square feet, although its shape need not be perfectly square. In a land survey, the entire amount of surface land is measured and the result calculated in acres. When you need to calculate a single acre from a lot or land, you’ll reverse the process.

    Establish a starting point to calculate a square acre. This is the outside corner where you want your acre to begin. Use a survey flag to mark the spot.

    Position the measuring wheel beside the survey stake and reset the counter to zero. Walk in a straight line, holding the measuring wheel steady with one hand, allowing it to roll smoothly over the terrain.

    Stop at the point where the measuring wheel reads 208.7 and set another survey flag in the ground at that spot. This is the first side of the square acre.

    Turn at a right angle and reset your measuring wheel to zero. Proceed to walk another 208.7 feet and place the third survey marker.

    Reset the measuring wheel to zero and walk another 208.7 feet to form the third side of the acre. Set your last survey flag at this point. The four flags now represent the four corners of a square acre.

    Calculate a rectangular acre instead of a square acre by determining the distance of one side of the rectangle. For instance, if you want to calculate an acre that is long and narrow, divide 43,560 by one side's measurement. The resulting number forms the adjacent sides of the rectangle.

    Divide 43,560 by 100 and you'll get 435.6. By using your measuring wheel, you can calculate an acre that measures 100 feet by 435.6 feet.


    • As long as the square feet within your acre measure 43.560 feet, the outside shape of your acre can be irregular.

      Acres are often not exact when recorded on deeds and property surveys. They may contain a few feet less or a few feet more than a full acre.


    • Avoid letting the wheel wobble. It must remain straight in order to give an accurate measurement.