Draw Size Gizmo - Unity

DrawSizeGizmo.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEditor;

[ExecuteInEditMode]
public class DrawSizeGizmo : MonoBehaviour {
	public bool enabled = true;

	void OnDrawGizmos () {
		if (!enabled)
			return;

		Vector3 size = this.GetComponent<Renderer> ().bounds.size;

		Gizmos.color = Color.red;
		Gizmos.DrawCube (
			transform.position - transform.up * size.y/2f + transform.forward * size.z/2f,
			new Vector3(size.x, 0.05f, 0.05f)
		);
		Handles.Label(
			transform.position - transform.up * size.y/2f + transform.forward * size.z/2f, 
			size.x.ToString() + "m"
		);

		Gizmos.color = Color.green;
		Gizmos.DrawCube (
			transform.position + transform.forward * size.z/2f + transform.right * size.x/2f,
			new Vector3(0.05f, size.y, 0.05f)
		);
		Handles.Label(
			transform.position + transform.forward * size.z/2f + transform.right * (size.x/2f - 0.1f),
			size.y.ToString() + "m"
		);

		Gizmos.color = Color.blue;
		Gizmos.DrawCube (
			transform.position - transform.up * size.y/2f + transform.right * size.x/2f,
			new Vector3(0.05f, 0.05f, size.z)
		);
		Handles.Label(
			transform.position - transform.up * size.y/2f + transform.right * (size.x/2f + 0.4f),
			size.z.ToString() + "m"
		);



	}

}

DrawSizeGizmo.gif