diff --git a/lib/isInViewport.js b/lib/isInViewport.js
index 9868df6..6bcc1aa 100644
--- a/lib/isInViewport.js
+++ b/lib/isInViewport.js
@@ -90,10 +90,10 @@
       var viewportRect = $viewport.get(0).getBoundingClientRect();
 
       //recalculate these relative to viewport
-      top    = top - viewportRect.top;
+      top = top - viewportRect.top;
       bottom = bottom - viewportRect.top;
-      left   = left - viewportRect.left;
-      right  = left + $viewportWidth;
+      left = left - viewportRect.left;
+      right = right - viewportRect.left;
 
       //get the scrollbar width from cache or calculate it
       isInViewport.scrollBarWidth = isInViewport.scrollBarWidth || getScrollbarWidth($viewport);
@@ -113,10 +113,12 @@
     //the element is NOT in viewport iff it is completely out of
     //viewport laterally or if it is completely out of the tolerance
     //region. Therefore, if it is partially in view then it is considered
-    //to be in the viewport and hence true is returned
+    //to be in the viewport and hence true is returned. Because we have adjusted
+    //the left/right positions relative to the viewport, we should check the
+    //element's right against the viewport's 0 (left side), and the element's
+    //left against the viewport's width to see if it is outside of the viewport.
 
-    //if the element is laterally outside the viewport
-    if (Math.abs(left) >= $viewportWidth)
+    if (right <= 0 || left >= $viewportWidth)
       return isVisibleFlag;
 
     //if the element is bound to some tolerance