An octagon is a shape with eight sides that are all the same length. By knowing the length of just one side of the shape, you can learn a great deal about the octagon's other properties, such as its area. Additionally, if you are dealing with a three-dimensional octagon, you can discover its volume with little information.
Multiply the length of one side of the octagon by itself.
Multiply the number you calculated in Step 1 by 4.8284. This is the area of the octagon.
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Multiply the area of the octagon by its depth to find its volume.