Equilateral Triangle Calculator

Your details

Pick which measurement you already know. The calculator will find all the others.
The length of one side. All three sides of an equilateral triangle are equal.
cm
Area
15.5885cm²
Height5.1962cm
Perimeter18cm
Semiperimeter9cm
Inradius (r)1.7321cm
Circumradius (R)3.4641cm
Side length (a)6cm

This equilateral triangle has an area of 15.59 cm² and a height of 5.2 cm.

  • The inradius is 1.7321 cm and the circumradius is 3.4641 cm. The circumradius is always exactly twice the inradius in an equilateral triangle.
  • Every side is 6 cm, so the perimeter is 18 cm.
  • Area grows with the square of the side, so doubling the side quadruples the area while the perimeter only doubles.

Next stepNeed the area of a triangle with three different side lengths? Use the triangle calculator with Heron's formula instead.

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