diff --git a/src/ol/extent.js b/src/ol/extent.js
index 3a00a840c9..c2e810acb5 100644
--- a/src/ol/extent.js
+++ b/src/ol/extent.js
@@ -423,6 +423,15 @@ ol.extent.getIntersectionArea = function(extent1, extent2) {
 };
 
 
+/**
+ * @param {ol.Extent} extent Extent.
+ * @return {number} Margin.
+ */
+ol.extent.getMargin = function(extent) {
+  return ol.extent.getWidth(extent) + ol.extent.getHeight(extent);
+};
+
+
 /**
  * @param {ol.Extent} extent Extent.
  * @return {ol.Size} Size.