Parallel sides and height
Trapezoid Area Calculator
Enter the lengths of the two parallel sides and the perpendicular distance between them.
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Average the parallel sides, then multiply by height
Use A = (a + b) × h ÷ 2, where a and b are the two parallel sides and h is the perpendicular distance between them. You can enter the parallel sides in either order.
Example: parallel sides 6 ft and 10 ft, height 4 ft
(6 + 10) × 4 ÷ 2 = 32 ft², or approximately 2.97 m².
Height is not the sloping edge
Measure straight across the gap between the parallel sides at a right angle. The non-parallel sides can be slanted and do not need to be equal. Their lengths alone do not replace the height.
A trapezoid is commonly called a trapezium in UK usage. The formula here applies to a quadrilateral with a pair of parallel sides. If both parallel side lengths are equal, the area formula reduces to side length × height.
Results are rounded for display. Calculations use unrounded values and international foot-based conversions. Enter actual lengths, rather than squared units.