Find the area, perimeter, and type of a triangle from its three sides. Enter the side lengths.
Area
— sq units
By Heron formula.Usage Tip
A 3-4-5 triangle is the classic right triangle, since 3² + 4² = 5².
THE MATH
Heron: s = (a+b+c)÷2, area = √(s(s−a)(s−b)(s−c))
Type from sides and from the Pythagorean comparison
Type from sides and from the Pythagorean comparison
Heron formula finds a triangle area from just its three sides, no height needed.
Comparing the longest side squared to the sum of the other squares tells whether it is right, acute, or obtuse.
Comparing the longest side squared to the sum of the other squares tells whether it is right, acute, or obtuse.
Each side must be shorter than the sum of the other two (triangle inequality).
Type by sides: equilateral, isosceles, or scalene.
Type by angles: right, acute, or obtuse.
Type by sides: equilateral, isosceles, or scalene.
Type by angles: right, acute, or obtuse.