Triangle Calculator

Use SSS side lengths to verify a triangle, calculate perimeter and Heron area, and find all angles and classifications. Calculate it clearly with Figur.

How the triangle calculator works

Use SSS side lengths to verify a triangle, calculate perimeter and Heron area, and find all angles and classifications.

Method and assumptions

Figur validates the triangle inequality for three sides (SSS), calculates perimeter and area with Heron's formula, and obtains angles in degrees using the law of cosines.

  • All three sides are positive finite lengths in the same unit.
  • Each side must be shorter than the sum of the other two.
  • Right, acute, or obtuse classification is derived from squared side lengths with a small numeric tolerance.

Sources and references

Worked example

Enter side lengths 3, 4, and 5.

The perimeter is 12, the area is 6, and the triangle is right scalene.

Frequently asked questions

What is the triangle inequality?

Each side must be shorter than the sum of the other two sides.

How are the angles calculated?

They are calculated in degrees with the law of cosines.

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