Trapezoid Calculator
Calculate the area and properties of a trapezoid.
The shape with one parallel pair
A trapezoid is a four-sided shape with one pair of parallel sides of different lengths. This calculates its area and related properties from the parallel sides and height, a common shape in geometry and construction.
Enter the parallel sides and height to find the area.
Averaging the parallel sides
The trapezoid area has an elegant logic: it is the average of the two parallel sides, multiplied by the height between them. Averaging the two parallel lengths effectively turns the trapezoid into an equivalent rectangle of that average width, whose area is easy. This also shows why the rectangle and triangle are special cases — a rectangle is a trapezoid whose parallel sides are equal, and a triangle is the limit where one parallel side shrinks to nothing. Trapezoids appear constantly in real structures, from the cross-sections of channels and embankments to architectural shapes, and the area calculation is also the basis of a numerical method for estimating the area under a curve by slicing it into thin trapezoids, which connects this simple shape to calculus.
Frequently asked questions
How is a trapezoid's area found?
Average the two parallel sides and multiply by the height between them — averaging the parallel lengths turns it into an equivalent rectangle.
How does it relate to rectangles and triangles?
A rectangle is a trapezoid with equal parallel sides, and a triangle is the limit where one parallel side shrinks to nothing.
Is anything uploaded?
No. The calculation happens in your browser.