How it is calculated
The midsegment of a trapezoid is half the sum of the bases. The area is that midsegment times the height. The sloping sides are needed only for the perimeter. They do not change the area.
S = (a + b) / 2 × h
Where the numbers come from
- Base a
- Base b
- Height
- Side c — Not required, only for the perimeter.
- Side d — Fill it in together with c.
Example
Bases 6 and 10, height 4. Area (6 + 10) / 2 × 4 = 32.
Questions
Is the height the slanted side?
No. The height is perpendicular to the bases. On an isosceles trapezoid a non-parallel side is longer than the height.
Does it work for a right trapezoid?
Yes, the formula does not care whether the corners are square.
Are the non-parallel sides required?
No. Leave them empty if you only need the perimeter.