A trapezoid is a four-sided shape with exactly one pair of parallel sides. This calculator finds its area, median, and perimeter from measurements you already have — no need to memorize the formulas or work through them by hand.
How the Trapezoid Calculator works
Area is computed with A = ½(a+b)·h, where a and b are the two parallel sides and h is the perpendicular height between them — the same formula taught in every geometry course. The median (or midsegment) is simpler still: it's just the average of the two bases, m = (a+b)/2, and it doesn't change no matter how tall or short the trapezoid is. Perimeter is the most literal calculation of the three — it's just the sum of all four sides, so it needs both leg lengths in addition to the bases.
Inputs and what they mean
Base 1 and Base 2 are the two parallel sides — they can be any positive lengths and in any unit, as long as you use the same unit for every input. Height must be the perpendicular distance between the bases, not the length of a slanted leg; mixing those up is the most common source of an incorrect area. Leg 1 and Leg 2 are optional — they only affect the Perimeter tab, so you can skip them entirely if you just need the area or median.
Limits and edge cases
This calculator assumes you already know the height as a straight-line perpendicular measurement. If you only know the leg lengths and the base lengths (not the height), you'll need trigonometry or a separate calculation to find the height first before this tool can compute the area. For an isosceles trapezoid — where the two legs are equal — enter the same value for both Leg 1 and Leg 2; the perimeter formula still applies unchanged.