In geometry, the area enclosed by a trapezoid is defined by this formula:
where a is the length of side a, b is the length of side b, and h is the height, measured at a right angle to the base. In Excel, the same formula can be represented like this:
So, for example, to calculate the area of a trapezoid where a is 3, b is 5, and h is 2, you can use a formula like this:
=(5+3)/2*2 // returns 8
In the example shown, the goal is to calculate the area for eleven trapezoids where a comes from column B, b is in column C, and h comes from column D. The formula in E5 is:
As this formula is copied down the table, it calculates a different area at each new row.
Note: The parentheses in this formula are optional and for readability only. In Excel's order of operations, multiplication will occur before division, so the parentheses are unnecessary.