Index: /CKEditor/trunk/CHANGES.html
===================================================================
--- /CKEditor/trunk/CHANGES.html	(revision 6920)
+++ /CKEditor/trunk/CHANGES.html	(revision 6921)
@@ -51,4 +51,5 @@
 		<li><a href="http://dev.ckeditor.com/ticket/6263">#6263</a> : Some of the table cell's context menu options may be incorrectly disabled.</li>
 		<li><a href="http://dev.ckeditor.com/ticket/6247">#6247</a> : Focus restores properly after float panel is closed.</li>
+		<li><a href="http://dev.ckeditor.com/ticket/7173">#7173</a> : Enhancement to "autogrow" plugin makes it more accurate on editor size.</li>
 		<li>Updated the following language files:<ul>
 			<li><a href="http://dev.ckeditor.com/ticket/7834">#7834</a> : Dutch;</li>
Index: /CKEditor/trunk/_source/plugins/autogrow/plugin.js
===================================================================
--- /CKEditor/trunk/_source/plugins/autogrow/plugin.js	(revision 6920)
+++ /CKEditor/trunk/_source/plugins/autogrow/plugin.js	(revision 6921)
@@ -8,38 +8,52 @@
  */
 (function(){
-	var resizeEditor = function( editor )
-	{
-		if ( !editor.window )
-			return;
-		var doc = editor.document,
-			currentHeight = editor.window.getViewPaneSize().height,
-			newHeight;
 
-		// We can not use documentElement to calculate the height for IE (#6061).
-		// It is not good for IE Quirks, yet using offsetHeight would also not work as expected (#6408).
-		// We do the same for FF because of the html height workaround (#6341).
-		if ( CKEDITOR.env.ie || CKEDITOR.env.gecko )
-			newHeight = doc.getBody().$.scrollHeight + ( CKEDITOR.env.ie && CKEDITOR.env.quirks ? 0 : 24 );
-		else
-			newHeight = doc.getDocumentElement().$.offsetHeight;
-
-		var min = editor.config.autoGrow_minHeight,
-			max = editor.config.autoGrow_maxHeight;
-		( min == undefined ) && ( editor.config.autoGrow_minHeight = min = 200 );
-		if ( min )
-			newHeight = Math.max( newHeight, min );
-		if ( max )
-			newHeight = Math.min( newHeight, max );
-
-		if ( newHeight != currentHeight )
-		{
-			newHeight = editor.fire( 'autoGrow', { currentHeight : currentHeight, newHeight : newHeight } ).newHeight;
-			editor.resize( editor.container.getStyle( 'width' ), newHeight, true );
-		}
-	};
 	CKEDITOR.plugins.add( 'autogrow',
 	{
 		init : function( editor )
 		{
+			var lastContentHeight;
+			var resizeEditor = function( editor )
+			{
+				if ( !editor.window )
+					return;
+
+				var doc = editor.document,
+					resizeable = editor.getResizable( 1 ),
+					body = doc.getBody().$,
+					htmlElement = doc.getDocumentElement().$,
+					currentHeight = resizeable.$.offsetHeight,
+					newHeight;
+
+				var delta =
+						// Delta height by checking scrollHeight.
+						( CKEDITOR.env.ie && CKEDITOR.env.quirks ? body.scrollHeight - body.clientHeight
+								: htmlElement.scrollHeight - ( htmlElement.clientHeight || htmlElement.offsetHeight ) )
+						// Negative scrollHeight (content reduced) is not supported in some browsers, figure it out by watching over the content size.
+						|| ( body.clientHeight < lastContentHeight ? body.clientHeight - lastContentHeight : 0 );
+
+				if ( delta )
+				{
+					newHeight = currentHeight + delta;
+					var min = editor.config.autoGrow_minHeight,
+						max = editor.config.autoGrow_maxHeight;
+
+					( min == undefined ) && ( editor.config.autoGrow_minHeight = min = 200 );
+					if ( min )
+						newHeight = Math.max( newHeight, min );
+					if ( max )
+						newHeight = Math.min( newHeight, max );
+
+					if ( newHeight != currentHeight )
+					{
+						newHeight = editor.fire( 'autoGrow', { currentHeight : currentHeight, newHeight : newHeight } ).newHeight;
+						resizeable.setStyle( 'height', newHeight + 'px' );
+						editor.fire( 'resize' );
+					}
+				}
+
+				lastContentHeight = body.clientHeight;
+			};
+
 			for ( var eventName in { contentDom:1, key:1, selectionChange:1, insertElement:1 } )
 			{
Index: /CKEditor/trunk/_source/themes/default/theme.js
===================================================================
--- /CKEditor/trunk/_source/themes/default/theme.js	(revision 6920)
+++ /CKEditor/trunk/_source/themes/default/theme.js	(revision 6921)
@@ -353,10 +353,11 @@
  * is mainly used by the resize plugin, which adds a UI handle that can be used
  * to resize the editor.
+ * @param {Boolean} forContents Whether to return the "contents" part of the theme instead of the container.
  * @returns {CKEDITOR.dom.element} The resizable element.
  * @example
  */
-CKEDITOR.editor.prototype.getResizable = function()
+CKEDITOR.editor.prototype.getResizable = function( forContents )
 {
-	return this.container;
+	return forContents ? CKEDITOR.document.getById( 'cke_contents_' + this.name ) : this.container;
 };