Right Trapezoid Calculator — Area, Perimeter & Angles
Enter the two parallel bases and the perpendicular height of a right trapezoid to find its area, perimeter, slant side, both diagonals and all interior angles.
units
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A = ½ × (a + b) × h
- 1
Sum the bases
a + b = 4 + 8 = 12 - 2
Area
½ × 12 × h = ½ × 12 × 5 = 30Standard trapezoid area: half the sum of the bases times the perpendicular height.
How does this calculator work?
A right trapezoid has bases a and b, perpendicular height h, and slant side c = √(h²+(b−a)²). Area = ½(a+b)h, Perimeter = a+b+h+c, diagonals = √(a²+h²) and √(b²+h²), with two 90° angles. Enter any three known values to compute all properties.
Formula
How this is calculated
A right trapezoid is a quadrilateral with exactly one pair of parallel sides (the two bases) and exactly two right angles, both at the endpoints of the perpendicular side. Name the shorter base a, the longer base b, and the perpendicular side h. The fourth side is the slant (or oblique) leg c, which connects the far end of the shorter base to the far end of the longer base.
The slant side is the hypotenuse of a right triangle with legs h and (b − a): c = √(h² + (b − a)²). Area is the standard trapezoid formula: A = ½(a + b)h — the average of the two bases multiplied by the height. Perimeter sums all four sides: P = a + b + h + c. The two diagonals cross the interior: one from the bottom-left corner to the top-right corner (length √(a² + h²)) and one from the bottom-right to the top-left (length √(b² + h²)).
The two right angles sit at both ends of the perpendicular leg h. The acute angle at the base of the slant is arctan(h ÷ (b − a)); the obtuse angle at the top of the slant is the supplement of that. All inputs must be positive and the two bases must differ; if a = b the shape degenerates into a rectangle.
Frequently asked questions
Exactly two — both at the endpoints of the perpendicular leg. This distinguishes it from a general trapezoid (no right angles) and a rectangle (four right angles).
Drop a perpendicular from the top-right corner to the bottom base; it meets the base at a distance (b − a) from the right end. The slant side c is the hypotenuse of the right triangle with legs h and (b − a): c = √(h² + (b − a)²).
No — the calculator automatically identifies the longer and shorter base regardless of which field you use. The results are the same either way.
Also known as
TG we-Calculate Editorial Team. (2026). Right Trapezoid Calculator — Area, Perimeter & Angles [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/right-trapezoid-calculator
TG we-Calculate Editorial Team. "Right Trapezoid Calculator — Area, Perimeter & Angles." TG we-Calculate. 2026. https://we-calculate.com/calculator/right-trapezoid-calculator.
TG we-Calculate Editorial Team, "Right Trapezoid Calculator — Area, Perimeter & Angles," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/right-trapezoid-calculator
@misc{wecalculate_right_trapezoid_calculator, title = {Right Trapezoid Calculator — Area, Perimeter & Angles}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/right-trapezoid-calculator}}, year = {2026}, note = {TG we-Calculate} }
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