Triangle Calculator
Compute the area of a triangle using three side lengths (Heron’s formula) or base and height.
Area from three sides (Heron)
Area from base and height
Tips: Use consistent units for all lengths. For Heron, enter all three sides.
FAQ
For a triangle with side lengths a, b, and c, let s = (a+b+c)/2. The area is √(s(s−a)(s−b)(s−c)). All sides must be positive and satisfy the triangle inequality.
If you know (or can measure) one side as the base and the perpendicular height to that base, area = ½ × base × height.
The sum of any two sides must be greater than the third. Otherwise the tool shows no valid area.