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Equilateral Triangle Calculator

Enter any one of the side length, height, perimeter, or area of an equilateral triangle and get all the other values at once. It also computes the inradius and circumradius.

Input

Enter any one of the side length, height, perimeter, or area of an equilateral triangle to compute all the other properties along with the inradius and circumradius.

Value to enter

Result

aha

Side a

10

Height h

8.6603

Perimeter L

30

Area S

43.3013

Inradius r

2.8868

Circumradius R

5.7735

Lengths are shown in the same unit you enter; the area is in that unit squared.

How it works

  • Enter any one of the side length a, height h, perimeter L, or area S. The tool first solves for the side a and then computes every other property from it.
  • It uses the formulas height h=(√3/2)a, perimeter L=3a, area S=(√3/4)a², inradius r=(√3/6)a, and circumradius R=(√3/3)a.
  • When you enter the height, the side is recovered as a=2h/√3; from the perimeter, a=L/3; from the area, a=√(4S/√3).
  • Lengths are shown in the same unit you enter (enter cm to get cm, m to get m). The area is in that unit squared.
  • An equilateral triangle has three sides of equal length and three interior angles that are all 60°.