Equilateral Triangle Calculator
Enter the side, height, area, perimeter, inradius or circumradius of an equilateral triangle to find the rest.
Change the values and press Calculate to work out your own figures.
Enter any one measurement.
Show the working
- From the side a
- The shape is fixed, so every measurement is a fixed multiple of the side
How to use it
Enter any one measurement.
Enter the values you know (decimals, fractions, surds such as 2√5, or angles such as π/3 in radians). Show the working gives the rule used at each step.
Key facts
h = (√3/2) a; A = (√3/4) a²; R = 2r
Centres coincide
In an equilateral triangle the centroid, incentre and circumcentre are the same point, and the circumradius is twice the inradius.
Questions
What is the area with side 3?
(9√3)/4 ≈ 3.897114317.
What is the height?
(√3/2) × side.
Formulas
h = (√3/2) a; A = (√3/4) a²; R = 2r
Sources
Limitations
- Angles can be typed in degrees or radians; radians may be written with π (π/3, 2pi/3).