Find the area and slant side length of a right trapezoid — one with a leg perpendicular to its two parallel bases.
How it works
Area follows the usual trapezoid formula: area = (b₁ + b₂) ÷ 2 × height. The slant side is the hypotenuse of the right triangle formed by the height and the difference between the two bases: slant = √(height² + (b₁ − b₂)²). Bases of 12 and 8 with a 5-unit perpendicular leg give an area of 50 and a slant side of about 6.40.
What this does not include
This is distinct from this site’s general trapezoid area calculator, which takes height as a direct input without solving for a missing side, and its isosceles trapezoid calculator, which assumes two equal slanted legs rather than one perpendicular leg.
How to use this calculator
- Enter the longer base.
- Enter the shorter base.
- Enter the height — the perpendicular leg’s length.
What makes a trapezoid a “right” trapezoid specifically?
It has exactly one pair of right angles, formed where the perpendicular leg meets the two parallel bases — the other leg is slanted, unlike a rectangle where both legs are perpendicular.
Why does the perpendicular leg double as the height?
Height is defined as the perpendicular distance between the two parallel bases, and a leg that’s already perpendicular to both bases is, by definition, exactly that distance.
Can a right trapezoid also be isosceles?
No — an isosceles trapezoid has two equal slanted legs by definition, while a right trapezoid has one perpendicular and one slanted leg, which can only be equal in the degenerate case of a rectangle.
