Área Trapézio Isósceles
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
A = (B+b)·h/2
About this calculator
The isosceles trapezoid area calculator uses the same formula as a regular trapezoid: area equals the sum of the bases (major and minor) multiplied by the height, divided by two. The difference is that in an isosceles trapezoid, the non-parallel sides are equal, which makes it easier to calculate the height when it is not directly provided. To use the tool, enter the values for the major base (B), minor base (b), and height (h) in the indicated fields. The result is displayed in square units, consistent with the input units.
This calculator is useful in practical situations such as engineering projects, architecture, furniture design, or even school geometry problems. For example, calculating the area of a trapezoidal roof, a piece of clothing, or a plot of land with an irregular shape. The formula is simple and straightforward, but common mistakes include confusing the major base with the minor base or using inconsistent units (meters with centimeters). Always ensure all measurements are in the same unit before calculating.
An important caution: the height must be perpendicular to the bases. In isosceles trapezoids, the height can be obtained from the slanted sides using the Pythagorean theorem if necessary. The calculator assumes you already have the height. Otherwise, you will need to calculate it beforehand. Also, remember that the formula is valid for any trapezoid, not just isosceles. The difference of this type is symmetry, which simplifies other calculations, such as the perimeter.
Frequently asked questions
What is the difference between an isosceles trapezoid and a right trapezoid?
In an isosceles trapezoid, the non-parallel sides are equal, and the base angles are congruent. In a right trapezoid, one side is perpendicular to the bases, forming two right angles.
Can I use this calculator for a trapezoid that is not isosceles?
Yes, the formula (B+b)*h/2 is the same for any trapezoid. The calculator works regardless of the type, as long as you provide the bases and height.
How do I calculate the height if it is not given?
For an isosceles trapezoid, the height can be found using the Pythagorean theorem: h = sqrt(L² - ((B-b)/2)²), where L is the length of the non-parallel side.
What happens if I use different units (meters and centimeters)?
The result will be incorrect. Convert all measurements to the same unit before entering. For example, if the major base is in meters and the height in centimeters, convert the height to meters.
Does the formula work if the minor base is larger than the major base?
No, the major base (B) should be the longer side. If you swap the values, the calculation still works mathematically because addition is commutative, but the result is the same. However, it is correct to use B for the larger base.