To calculate the area of a trapezoid, identify the measurements of the two parallel sides and the distance between them. Put those numbers into the formula for calculating the area of a trapezium, and solve the equation.

**Find the lengths of the two parallel sides**In some cases, the length of the two sides might be given as part of the problem. In other circumstances, the lengths may need to be calculated from other information. The lengths of the other two, nonparallel sides are not necessary to calculate the area.

**Find the distance between the two parallel sides**This measurement is also called the height of the trapezoid. In some cases, this measurement is given as part of the problem. At other times, it might need to be calculated from other information given about the figure.

**Put these three measurements into the correct formula**The formula for calculating the area of the trapezoid is quite simple: 1/2 x (a+b) x height, where "a" and "b" are the lengths of the two parallel sides. To put this into words, add the lengths of the two parallel sides together, and divide it in half. Then, multiply that answer by the height of the trapezoid. The resulting answer is the area of the trapezoid.