Triangle Calculator
Calculate triangle area and perimeter from three sides — nothing is uploaded.
Triangle area with Heron’s formula
Enter the three side lengths and instantly get the area and perimeter. The calculator uses Heron’s formula: given semi-perimeter s = (a+b+c)/2, area = √(s(s−a)(s−b)(s−c)).
The triangle inequality is checked automatically — if it fails you get an error instead of a nonsense result.
FAQ
What is Heron’s formula? A formula that computes triangle area from side lengths alone, without needing the height.