How do I find the area if I only know the three sides?

Use Heron's formula: s = (a+b+c)/2; Area = √(s(s-a)(s-b)(s-c)), where a, b, c are the side lengths and s is the semi-perimeter.

What is an equilateral triangle area formula?

For an equilateral triangle with side length a: Area = (√3/4) × a². This is a simplified version of the base-height formula when all sides are equal.

What is the area of a right triangle?

For a right triangle, the two legs are the base and height. Area = ½ × leg₁ × leg₂. For example, a 3-4-5 triangle has area = ½ × 3 × 4 = 6 square units.

Triangle Area Calculator

The Triangle Area Calculator computes the area of a triangle using the base and height method: Area = ½ × base × height. This is the simplest and most common formula for finding triangle area. For triangles where the height is unknown, Heron's formula (using all three sides) can be used instead.

Base

Height (perpendicular to base)

How to Use This Calculator

1
Enter the base length of the triangle.
2
Enter the perpendicular height (measured from the base to the opposite vertex at a right angle).
3
Click Calculate to see the area.

Frequently Asked Questions

Area = ½ × base × height. The height must be the perpendicular height — the straight vertical distance from the base to the opposite vertex, not the slant side.

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