About the trapezoid calculator
A trapezoid (trapezium in British English) has one pair of parallel sides, the bases a and b. The area only needs the two bases and the height, so you get it as soon as those three are known. The legs and angles need one more value.
Four measurements fix a general trapezoid. Any four work, including all four sides, which the calculator solves numerically.
Formulas
| Area | K = (a + b)·h/2 |
| Midsegment | m = (a + b)/2 |
| Legs | c = h/sin α, d = h/sin β |
| Perimeter | P = a + b + c + d |
Frequently asked questions
How do I calculate the area of a trapezoid?
Average the two parallel bases and multiply by the height: K = (a + b)/2 · h.
Can I find a trapezoid from its four sides?
Yes, enter a, b, c and d. The calculator finds the height and angles numerically (a trapezoid with given sides is unique when a ≠ b).