diff --git a/lib/ComicBook.js b/lib/ComicBook.js
index 9fe9b9f..d2e447d 100755
--- a/lib/ComicBook.js
+++ b/lib/ComicBook.js
@@ -76,7 +76,7 @@ var ComicBook = (function ($) {
 
     var defaults = {
       displayMode: 'double',  // single / double
-      zoomMode: 'fitWidth', // manual / fitWidth
+      zoomMode: 'fitWindow', // manual / fitWidth / fitWindow
       manga: false,     // true / false
       enhance: {},
       keyboard: {
@@ -338,7 +338,12 @@ var ComicBook = (function ($) {
 
     ComicBook.prototype.fitWidth = function () {
       options.zoomMode = 'fitWidth';
-      ComicBook.prototype.drawPage();
+      self.drawPage();
+    };
+
+    ComicBook.prototype.fitWindow = function () {
+      options.zoomMode = 'fitWindow';
+      self.drawPage();
     };
 
     /**
@@ -465,7 +470,7 @@ var ComicBook = (function ($) {
         throw ComicBookException.INVALID_PAGE_TYPE + ' ' + typeof page;
       }
 
-      var width = page.width;
+      var width = page.width, height = page.height;
 
       // reset the canvas to stop duplicate pages showing
       canvas.width = 0;
@@ -507,6 +512,21 @@ var ComicBook = (function ($) {
         scale = zoom_scale;
         break;
 
+      case 'fitWindow':
+        document.body.style.overflowX = 'hidden';
+
+        var width_scale = (windowWidth() > width) ?
+          ((windowWidth() - width) / windowWidth()) + 1 // scale up if the window is wider than the page
+          : windowWidth() / width; // scale down if the window is narrower than the page
+        var windowHeight = window.innerHeight;
+        var height_scale = (windowHeight > height) ?
+          ((windowHeight - height) / windowHeight) + 1 // scale up if the window is wider than the page
+          : windowHeight / height; // scale down if the window is narrower than the page
+
+        zoom_scale = (width_scale > height_scale) ? height_scale : width_scale;
+        scale = zoom_scale;
+        break;
+
       default:
         throw ComicBookException.INVALID_ZOOM_MODE + ' ' + options.zoomMode;
       }
@@ -569,6 +589,7 @@ var ComicBook = (function ($) {
 
       // disable the fit width button if needed
       $('button.cb-fit-width').attr('disabled', (options.zoomMode === 'fitWidth'));
+      $('button.cb-fit-window').attr('disabled', (options.zoomMode === 'fitWindow'));
 
       // disable prev/next buttons if not needed
       $('.navigate').show();
diff --git a/templates/toolbar.handlebars b/templates/toolbar.handlebars
index d6704d7..5f47a2b 100644
--- a/templates/toolbar.handlebars
+++ b/templates/toolbar.handlebars
@@ -47,6 +47,9 @@
 		<li>
 			<button data-trigger="click" data-action="fitWidth" title="fit page to window width" class="icon-expand"></button>
 		</li>
+		<li>
+			<button data-trigger="click" data-action="fitWindow" title="fit page to window" class="icon-expand-2"></button>
+		</li>
 		<li>
 			<button data-trigger="click" data-action="toggleReadingMode" title="switch reading direction" class="icon-arrow-right-3 manga-false"></button>
 			<button data-trigger="click" data-action="toggleReadingMode" title="switch reading direction" class="icon-arrow-left-3 manga-true"></button>