Triangle type calculator
Enter three sides to classify the triangle by sides and by angles in one step, after checking that they form a triangle.
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Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Enter side a, side b and side c.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
By sides: compare the lengths. By angles: with c the longest side, a² + b² = c² means right, a² + b² > c² acute, and a² + b² < c² obtuse.
Example
Inputs: Side a = 5, Side b = 5, Side c = 8. Result: By sides: Isosceles; By angles: Obtuse; Largest angle: 106.2602 °.
Limits and caveats
- Rounded lengths can make a right triangle show as slightly acute or obtuse, so check the largest angle.
Questions about this tool
What is the difference between isosceles and equilateral?
Isosceles has at least two equal sides. Equilateral has all three equal, with every angle 60 degrees.
How can I tell a triangle is obtuse from its sides?
If the square of the longest side is larger than the sum of the squares of the other two, it is obtuse.
Can a triangle be both right and isosceles?
Yes, the 45-45-90 triangle has two equal legs and a right angle.