Version: 2017.3
public static GUILayoutOption Height (float height);


Option passed to a control to give it an absolute height.

Note: This option will override the Automatic height Layout parameter

Fixed Height for a GUI Control.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour { void OnGUI() { GUILayout.Button("A Button with fixed height", GUILayout.Height(300)); } }