Mathf.PI

Description

The well-known 3.14159265358979... value (Read Only).

The ratio of the circumference of a circle to its diameter. Note that this value is a 32-bit floating point number i.e. a float. Approximately seven digits of precision are provided.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour
{
    public float radius = 5;

    void Start()
    {
        float perimeter = 2.0f * Mathf.PI * radius;
        Debug.Log("The perimeter of the circle is: " + perimeter);
    }
}