Triangle Calculator
Enter the three sides of a triangle to get its area, perimeter and type.
Show solution steps
What is the Triangle Calculator?
A triangle calculator finds a triangle's area and perimeter from its three side lengths, and identifies whether it's equilateral, isosceles or scalene.
How to Calculate
The area uses Heron's formula: with s = perimeter ÷ 2, area = √(s(s−a)(s−b)(s−c)). The sides must satisfy the triangle inequality.
Formula
Area = √(s(s−a)(s−b)(s−c)), where s = (a+b+c)/2
How to Use
- Enter your details in the fields above.
- The result updates instantly as you type.
- Use Copy, Print or Download PDF to save your result.
Frequently Asked Questions
Why do some side lengths give an error?
A triangle can only exist if each side is shorter than the sum of the other two (the triangle inequality). If not, no triangle is possible.
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