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Isosceles Trapezoid Calculator.

Calculate height, area, and perimeter from both bases and the equal leg.

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Set your values

Results update as you type.

Height: 4.582576 units

Height

0.000000units
Area: 45.825757 units²

Area

0.000000units²
Perimeter: 30 units

Perimeter

0.000000units
Equal leg: 5 units

Equal leg

0.000000units

Results update automatically as you type.

Use Cases

Geometry homework and exams

Quickly verify your manual calculations for isosceles trapezoid problems, ensuring accuracy in height, area, and perimeter.

Example: Check your answer for a trapezoid with bases 10 and 6, and leg 5.

Design and construction planning

Determine the dimensions and material needs for structures with isosceles trapezoid shapes, such as roof trusses or decorative elements.

Example: Calculate the area of a trapezoidal garden bed with bases 8 ft and 4 ft, and equal sides 3 ft.

Frequently Asked Questions

How do I calculate the height of an isosceles trapezoid?
Enter the lengths of the two bases (Base a and Base b) and the equal leg length. The calculator uses the formula: height = sqrt(leg^2 - ((base a - base b)^2)/4).
What is the formula for the area of an isosceles trapezoid?
The area is calculated as (1/2) * (Base a + Base b) * height. The height is derived from the leg length and the difference between the bases.
Can I use this calculator for any trapezoid?
No, this calculator is specifically for isosceles trapezoids, where the non-parallel sides (legs) are equal in length. For other trapezoids, you need different inputs.

Tips & Common Mistakes

Tips

  • Ensure all input values are in the same unit (e.g., all in meters or all in feet) to get consistent results.
  • The leg length must be greater than half the difference between the bases; otherwise, the trapezoid is invalid.
  • Double-check your base values: Base a and Base b are the parallel sides, and they can be in any order.
  • Use the perimeter result to estimate the total boundary length, which is useful for fencing or framing.

Common Mistakes to Avoid

  • Entering the leg length as the height directly; the height is calculated from the leg and base difference.
  • Using different units for the bases and leg, leading to incorrect results.
  • Assuming the calculator works for non-isosceles trapezoids; it only applies when the legs are equal.

Last updated: August 13, 2026