Calculator tool
How this calculator works
Use the explanation to understand the formula, assumptions, and practical limits behind the calculator result.
Three Sides Can Describe One Triangle
Before doing any geometry, the calculator checks whether the three sides can really form a triangle. Every pair of sides must add to more than the third side.
A Simple Check
Sides 3, 4, 5 form a valid triangle because every pair passes the rule. Sides 2, 3, 5 do not, because instead of being greater than 5.
How Area Is Found
Once the sides are valid, the calculator uses Heron's formula:
where is the semiperimeter.
How to Read the Result
Equal sides produce equilateral or isosceles labels, while three different side lengths produce scalene. The calculator also derives the angles, which helps show whether the triangle is acute, right, or obtuse.
Frequently asked questions
What is the triangle inequality?
For a real triangle, the sum of any two sides must be greater than the third side.
What does Heron's formula need?
It needs all three side lengths and the semiperimeter. No separate height input is required.
How does the calculator classify the triangle?
Three equal sides make an equilateral triangle, two equal sides make an isosceles triangle, and three different sides make a scalene triangle.
How does it know whether the triangle is right?
After calculating the angles, it checks whether one angle is effectively 90 degrees within a small tolerance.
