Calculate area, perimeter, and triangle type using Heron's formula. Perfect for geometry, surveying, engineering, and educational purposes.
Enter three side lengths to calculate triangle properties
Triangles are fundamental shapes in geometry, mathematics, engineering, and architecture. They are the simplest polygon and the only rigid polygon - their shape cannot change without changing side lengths. Understanding triangle calculations is essential for construction, surveying, navigation, computer graphics, and many other fields.
Heron's formula (also called Hero's formula) is a remarkable method for calculating a triangle's area using only the three side lengths. First, calculate the semi-perimeter s = (a + b + c) / 2. Then, the area is A = √[s(s-a)(s-b)(s-c)]. Named after Hero of Alexandria (circa 60 AD), this formula is elegant, efficient, and works for any triangle. It's particularly valuable when you know distances but not angles or heights.
Triangles are classified by their sides and angles. By sides: Equilateral triangles have all three sides equal, Isosceles triangles have two equal sides, and Scalene triangles have all different sides. By angles: Right triangles have one 90° angle, Acute triangles have all angles less than 90°, and Obtuse triangles have one angle greater than 90°. Our calculator automatically identifies the triangle type based on the side lengths you provide.
The triangle inequality theorem is fundamental: The sum of any two sides must be greater than the third side. This must hold for all three combinations. For example, sides 3, 4, 5 form a valid triangle (3+4>5, 3+5>4, 4+5>3), but sides 1, 2, 10 do not (1+2 is not greater than 10). Our calculator validates this automatically to ensure you're working with a real triangle.
“This triangle calculator is essential for my surveying work. Heron's formula calculation is perfect for triangulating land parcels when I have measured distances. The triangle type classification helps me quickly identify right angles in the field.”
“Excellent teaching tool! My students love seeing how changing side lengths affects the triangle type. The visual chart and clear formulas make abstract concepts concrete. The triangle inequality validation is a great learning moment.”
“I use this calculator for quick triangular truss calculations. The ability to identify right triangles automatically saves time in structural analysis. Accurate, fast, and the calculation history feature is incredibly useful for comparing designs.”
Love using our calculator?