△ Geometry
Triangle Calculator — Area, Perimeter, Angles
Calculate triangle area, perimeter, and all angles. Supports SSS (3 sides), SAS (2 sides + angle), ASA (2 angles + side), and right triangle (Pythagorean theorem).
Frequently Asked Questions
How do I calculate the area of a triangle? +
Use Heron's formula: Area = √(s(s-a)(s-b)(s-c)) where s = (a+b+c)/2. Or if you know base and height: Area = (base × height) / 2.
What is the Pythagorean theorem? +
For a right triangle: a² + b² = c², where c is the hypotenuse (longest side opposite the right angle). Use our Right Triangle tab to automatically calculate the missing side.
How do I find angles when I only know the sides? +
Use the Law of Cosines: cos(A) = (b² + c² − a²) / (2bc). Enter all three sides in the SSS tab and all angles will be calculated automatically.