Index: src/wp-includes/css/media-views.css
===================================================================
--- src/wp-includes/css/media-views.css	(revision 29289)
+++ src/wp-includes/css/media-views.css	(working copy)
@@ -1006,6 +1006,14 @@
 	outline: none;
 }
 
+.attachments-browser .attachments {
+	padding: 0;
+}
+
+.mode-select .attachments-browser .attachments {
+	padding: 0 16px;
+}
+
 .attachments-browser .uploader-inline:not(.hidden) + .attachments {
 	top: 350px;
 }
Index: src/wp-includes/js/media-views.js
===================================================================
--- src/wp-includes/js/media-views.js	(revision 29289)
+++ src/wp-includes/js/media-views.js	(working copy)
@@ -5267,6 +5267,7 @@
 			media.view.Attachments.$head().append( this.cssTemplate({
 				id:     this.el.id,
 				edge:   this.edge(),
+				columns: this.columns(),
 				gutter: this.model.get('gutter')
 			}) );
 		},
@@ -5282,12 +5283,29 @@
 			}
 
 			gutter  = this.model.get('gutter') * 2;
-			width   = this.$el.width() - gutter;
+			width   = this.$el.width() - gutter/2;
 			columns = Math.ceil( width / ( edge + gutter ) );
-			edge = Math.floor( ( width - ( columns * gutter ) ) / columns );
+			edge = Math.floor( ( width - ( ( columns - 1 ) * gutter ) ) / columns );
 			return edge;
 		},
 
+		/**
+		 * @returns {Number}
+		 */
+		columns: function() {
+			var edge = this.model.get('edge'),
+				gutter, width, columns;
+
+			if ( ! this.$el.is(':visible') ) {
+				return columns;
+			}
+
+			gutter  = this.model.get('gutter') * 2;
+			width   = this.$el.width() - gutter/2;
+			columns = Math.ceil( width / ( edge + gutter ) );
+			return columns;
+		},
+
 		initSortable: function() {
 			var collection = this.collection;
 
Index: src/wp-includes/media-template.php
===================================================================
--- src/wp-includes/media-template.php	(revision 29289)
+++ src/wp-includes/media-template.php	(working copy)
@@ -819,15 +819,15 @@
 
 	<script type="text/html" id="tmpl-attachments-css">
 		<style type="text/css" id="{{ data.id }}-css">
-			#{{ data.id }} {
-				padding: 0 {{ data.gutter }}px;
-			}
-
 			#{{ data.id }} .attachment {
 				margin: {{ data.gutter }}px;
 				width: {{ data.edge }}px;
 			}
 
+			#{{ data.id }} .attachment:nth-of-type({{ data.columns }}n+1) {
+				margin-left: 0;
+			}
+
 			#{{ data.id }} .attachment-preview,
 			#{{ data.id }} .attachment-preview .thumbnail {
 				width: {{ data.edge }}px;