# Equilateral Triangle Calculator

URL: https://speedycalculator.com/calculators/math/equilateral-triangle/
Last updated: 2026-10-25

> The equilateral triangle calculator finds the height, area, perimeter and the radii of the inscribed and circumscribed circles from the side length. Type an area to solve for the side.

## Inputs

- Side length (m, cm, mm, km, in, ft, yd, mi)

## Results

- Area
- Height
- Perimeter
- Inradius
- Circumradius

## Formula

```
h = √3 ÷ 2 × a
Area = √3 ÷ 4 × a²
```

## Explanation

All three sides and angles of an equilateral triangle are equal, so one measurement defines everything.

### How to use the Equilateral Triangle Calculator

- **Side length**
- Want to work backwards? Type a value into **Area** and **Side length** is calculated for you.

Results update as you type, and every field accepts the units shown in its menu.

### How it works

The height comes from splitting the triangle into two 30-60-90 triangles.

### What each result means

- **Area** = sqrt(3)÷4 × [Side length]^2
- **Height** = sqrt(3)÷2 × [Side length]
- **Perimeter** = 3×[Side length]
- **Inradius** = [Side length] ÷ (2×sqrt(3))
- **Circumradius** = [Side length] ÷ sqrt(3)

### Example values

How the main result changes when **Side length** changes and everything else stays at the example values above:

Side length (m)Area (m²)510.837.524.361043.312.567.661597.4320173.21

## Worked example

Inputs — Side length: 10 m.

Results — **Area = 43.3 m²**; Height = 8.66 m; Perimeter = 30 m; Inradius = 2.89 m; Circumradius = 5.77 m.

## FAQ

**What are the angles?**
Each is 60°.

**How is it related to a hexagon?**
A regular hexagon is made of six equilateral triangles.

**What formula does the Equilateral Triangle Calculator use?**
h = √3 ÷ 2 × a.

**Can I work backwards from the result?**
Yes. Type the result you want into Area and the calculator finds the matching side length.