This page describes how to derive the formula for the area of a parallelogram. It works by moving a piece of the parallelogram so as to make a rectangle with the same area, which is easier to calculate.
Click on the "Run" button below to see this in action.
This rearranging has created a rectangle whose area is clearly the same as the original parallelogram.
Recall that the
area of a rectangle is found by multiplying its width times its height. The area of the original parallelogram is therefore
w is the width, or length of a base, and
h is the altitude (height) of the parallelogram.