How do I find a trapezoid's area?
Average the two parallel sides, then multiply by the height: half of (a + b) times h. The height is the perpendicular gap between the parallel sides.
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Trapezoid Area Calculator
Find the area and perimeter of a trapezoid (trapezium) from its two parallel sides, height and the two slanted sides.
area = ½(a+b)×h ; perimeter = a+b+c+d
Frequently asked questions
What is a trapezoid (or trapezium)?
A four-sided shape with exactly one pair of parallel sides. The names vary by country, but the shape and formula are the same.
Why average the parallel sides?
Because the shape is wider at one parallel side than the other. Averaging them gives the equivalent width of a rectangle with the same area.
How is the perimeter calculated?
Just add all four sides together: the two parallel sides plus the two slanted legs. You need all four lengths for the perimeter.
Where is it used?
Cross-sections of canals and embankments, table tops, roof trusses, and any tapering panel in design and construction.