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Area of a trapezoid

Excel formula: Area of a trapezoid
Generic formula 

To calculate the area of a trapezoid in Excel, you can use a standard formula, adapted to for Excel's math operators. In the example shown, the formula in E5, copied down, is:


which calculates the area of a trapezoid given the length of side a in column B, the length of side b in column C, and the height (h) in column D.


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.

Dave Bruns

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