Trapezoid Area Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/5/2026
The area of a trapezoid is calculated as A = ((long base + short base) ÷ 2) × height. For a long base of 10 m, a short base of 6 m, and a height of 4 m, the area is 32 m².
Explanation
A trapezoid is a quadrilateral with two parallel sides, called bases (the long base and the short base), and two non-parallel sides. Its area is calculated as the average of the two bases, multiplied by the height — the perpendicular distance separating the two parallel bases, not to be confused with the length of the slanted sides connecting them. This formula is intuitive to understand by imagining a rectangle whose width would be the average of the trapezoid's two bases: a trapezoid has exactly the same area as a rectangle of that average width and the same height. It also generalizes the special case of a triangle (a short base reduced to zero gives a triangle, as shown by the edge case tested) and approaches a rectangle or parallelogram when the two bases are equal, the formula then simply reducing to base × height. Trapezoids appear frequently in practice: the cross-section of a ditch or an embankment, the shape of a plot of land, or the profile of a mechanical part. For the area of a circle rather than a trapezoid, see our circle area and circumference calculator; for a triangle, our triangle area calculator.
Example: long base 10 m, short base 6 m, height 4 m
Inputs
Long base: 10 m. Short base: 6 m. Height: 4 m.
Calculation
Area = ((10 + 6) ÷ 2) × 4 = (16 ÷ 2) × 4 = 8 × 4 = 32 m².
Result
The area of this trapezoid is 32 m².
Frequently asked questions
What's the difference between the height and the slanted sides of a trapezoid?
The height is the perpendicular distance between the two parallel bases, measured at a right angle — it's the only value to use in this formula. The slanted sides (the two non-parallel sides connecting the bases) generally have a different length than the height, except in the special case of a right trapezoid where one of the slanted sides happens to be perpendicular to the bases.
What happens if the two bases are equal?
If the long base and the short base have the same length, the shape is no longer really a trapezoid but a parallelogram (or a rectangle if the angles are right angles), and the formula naturally simplifies to base × height, exactly the area formula for a rectangle or a parallelogram.
Does this formula work for any shape of trapezoid?
Yes, the formula ((long base + short base) ÷ 2) × height is valid for any trapezoid, whether isosceles (both slanted sides the same length), right-angled (one side perpendicular to the bases), or irregular: only the length of the two parallel bases and the height (perpendicular distance between them) enter the calculation, not the exact shape of the slanted sides.