Camera.allCamerasCount

Description

The number of cameras in the current Scene.

Returns the size of the array that Camera.allCameras returns and the amount of cameras that Camera.GetAllCameras will fill.

using UnityEngine;

public class ExampleScript : MonoBehaviour
{
    private int count;

    void Start()
    {
        count = Camera.allCamerasCount;
        print("We've got " + count + " cameras");
    }
}