Triangle calculator
Enter the three sides of a triangle to get its area, perimeter, angles and type.
About this calculator
The area comes from Heron's formula, and the angles from the law of cosines. The calculator also tells you if the triangle is equilateral, isosceles, scalene or right-angled.
Any two sides must add up to more than the third, otherwise the triangle cannot exist.
Common questions
What is Heron's formula?
It finds the area from the three sides: with s as half the perimeter, area = √(s(s−a)(s−b)(s−c)).
Why does it say the triangle cannot exist?
The two shorter sides must be longer together than the longest side.
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