function CalcSize (content : GUIContent) : Vector2

Description

Calculate the size of a some content if it is rendered with this style.

This function does not take wordwrapping into account. To do that, you need to determine the allocated width and then call CalcHeight to figure out the wordwrapped height.

    // Simple custom editor that when any SimpleExampleScript
    // is detected in the inspector, it shows it as an IntSlider
    // and a GUILayouted bar.
    
    @CustomEditor(SimpleExampleScript)
    class CustomEditorExample extends Editor {
    
        function OnInspectorGUI() {
            // Get the place of the next available position in the script
            target.damage = EditorGUILayout.IntSlider("Damage:",target.damage,1,100);
            ProgressBar (target.damage / 100.0, "Damage");
            
            target.armor = EditorGUILayout.IntSlider("Armor:",target.armor,1,100);
            ProgressBar (target.armor / 100.0, "Armor");
            
        }
        
        // Custom GUILayout progress bar.
        function ProgressBar (value : float, label : String) {
            var size : Vector2 = GUI.skin.GetStyle("ProgressBarText").CalcSize(GUIContent(label));
            var rect : Rect = GUILayoutUtility.GetRect (size.x, Mathf.Max(size.y));
            rect = Rect(rect.x + 4, rect.y, rect.width -8, rect.height);
            EditorGUI.ProgressBar (rect, value, label);
            EditorGUILayout.Space();
        }
    }

And the script attached to this editor script:

    // SimpleExampleScript.js
    // This is not an editor script.
    
    var armor : int = 75;
    var damage : int = 25;