Right Trapezoid Area Calculator — Step-by-Step
Enter the two parallel bases and the perpendicular height of a right trapezoid to compute its area instantly — with a clear step-by-step derivation of the formula.
units
units
units
A = ½ × (a + b) × h
Identify the two parallel bases
Sum the bases
Multiply by the perpendicular height h
Divide by 2 — the trapezoid equals half the surrounding rectangle
- 1
Sum the bases
a + b = 3 + 7 = 10 - 2
Average of bases
(a + b) ÷ 2 = 10 ÷ 2 = 5 - 3
Area
5 × h = 5 × 4 = 20Area equals the midline (average base) multiplied by the perpendicular height.
How does this calculator work?
Area of a right trapezoid = ½ × (a + b) × h, where a and b are the two parallel sides and h is the perpendicular distance between them. Enter all three values to get the area instantly; the step-by-step breakdown shows exactly how the formula is applied.
Formula
How this is calculated
A right trapezoid has two parallel sides called bases (a and b) and a perpendicular side h that connects them at right angles. The area formula A = ½(a + b)h is identical to the general trapezoid area formula: it works because a trapezoid is exactly half of a parallelogram formed by doubling it. The average of the two bases, (a + b)/2, gives the length of the median (midline) — the segment parallel to the bases at their midpoint — and multiplying by the height h gives the area.
Geometrically, the area equals the area of a rectangle with the median length and the height h. Because a right trapezoid has one side that is perpendicular to both bases, the height h is simply that perpendicular leg itself — no trigonometry is needed to find it.
The calculator also computes the slant side c = √(h² + (b − a)²), which is the hypotenuse of the right triangle formed by h and the horizontal offset (b − a), and the perimeter as the sum of all four sides. All inputs must be positive; the two bases may be equal (giving a rectangle) or unequal.
Frequently asked questions
Place two identical trapezoids together (one flipped) to form a parallelogram with base (a + b) and height h. The trapezoid is half that parallelogram, so its area is ½(a+b)h. Equivalently, (a+b)/2 is the midline length, and area = midline × height.
A right trapezoid has exactly two right angles — both at the endpoints of the perpendicular leg h. The perpendicular leg stands at 90° to both parallel bases, so h is the shortest route between them and equals the true height directly, without needing any angle calculation.
Yes: rearrange the formula. To find the missing base: a = (2A/h) − b. To find height: h = 2A/(a+b). These rearrangements are algebraically exact. A dedicated solver for the full set of trapezoid properties is available in the Right Trapezoid Calculator.
Also known as
TG we-Calculate Editorial Team. (2026). Right Trapezoid Area Calculator — Step-by-Step [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/right-trapezoid-area-calculator
TG we-Calculate Editorial Team. "Right Trapezoid Area Calculator — Step-by-Step." TG we-Calculate. 2026. https://we-calculate.com/calculator/right-trapezoid-area-calculator.
TG we-Calculate Editorial Team, "Right Trapezoid Area Calculator — Step-by-Step," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/right-trapezoid-area-calculator
@misc{wecalculate_right_trapezoid_area_calculator, title = {Right Trapezoid Area Calculator — Step-by-Step}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/right-trapezoid-area-calculator}}, year = {2026}, note = {TG we-Calculate} }
Did this calculator help you?