diff --git a/scrollbarWidth.js b/scrollbarWidth.js
index 94a549f..d72c670 100644
--- a/scrollbarWidth.js
+++ b/scrollbarWidth.js
@@ -1,3 +1,17 @@
-function getScrollbarWidth() {
-  return window.innerWidth - document.documentElement.clientWidth;
+/** based off of https://stackoverflow.com/questions/13382516/getting-scroll-bar-width-using-javascript */
+function getScrollbarWidth(container = document.body) {
+  const invisibleParent = document.createElement('div');
+  invisibleParent.style.visibility = 'hidden';
+  invisibleParent.style.overflow = 'scroll'; // force scrollbar to appear
+  invisibleParent.style.msOverflowStyle = 'scrollbar'; // needed for WinJS apps
+  container.appendChild(invisibleParent);
+  
+  const child = document.createElement('div');
+  invisibleParent.appendChild(child);
+  
+  const scrollbarWidth = invisibleParent.offsetWidth - child.offsetWidth;
+  
+  invisibleParent.parentNode.removeChild(invisibleParent);
+  
+  return scrollbarWidth;
 }