6.G.A.1 Google Classroom About Transcript Area of a trapezoid is found with the formula, A= (a+b)h/2. To find the area of a trapezoid, you need to know the lengths of the two parallel sides (the "bases") and the height. Add the lengths of the two bases together, and then multiply by the height. Finally, divide by 2 to get the area of the trapezoid.