Equilateral triangle calculator
All sides of an equilateral triangle are equal and every angle is 60°, so one side length gives every measurement.
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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 length and length unit.
- 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
Area = (√3 ÷ 4) × a², height = (√3 ÷ 2) × a, inradius = a ÷ (2√3) and circumradius = a ÷ √3.
Example
Inputs: Side length = 6, Length unit = Centimeters (cm). Result: Area: 15.5885 cm²; Height: 5.1962 cm; Perimeter: 18 cm.
Limits and caveats
- It applies only to equilateral triangles; for others use Heron's formula.
- The unit choice only labels the results.
Questions about this tool
What is the area formula for an equilateral triangle?
Area equals √3 ÷ 4 times the side squared, about 0.433 × a².
How tall is an equilateral triangle with side 6?
Height = (√3 ÷ 2) × 6, about 5.196.
How do the inradius and circumradius compare?
In an equilateral triangle the circumradius is exactly twice the inradius.