diff --git a/src/ol/geom/linearring.js b/src/ol/geom/linearring.js
index 64a5bb6194..14a72b383d 100644
--- a/src/ol/geom/linearring.js
+++ b/src/ol/geom/linearring.js
@@ -76,7 +76,7 @@ ol.geom.LinearRing.prototype.closestPointXY =
 
 
 /**
- * @return {number} Area.
+ * @return {number} Area (on projected plane).
  * @api
  */
 ol.geom.LinearRing.prototype.getArea = function() {
diff --git a/src/ol/geom/linestring.js b/src/ol/geom/linestring.js
index f0c089843e..b6cf7d4dfa 100644
--- a/src/ol/geom/linestring.js
+++ b/src/ol/geom/linestring.js
@@ -141,7 +141,7 @@ ol.geom.LineString.prototype.getCoordinates = function() {
 
 
 /**
- * @return {number} Length.
+ * @return {number} Length (on projected plane).
  * @api
  */
 ol.geom.LineString.prototype.getLength = function() {
diff --git a/src/ol/geom/multipolygon.js b/src/ol/geom/multipolygon.js
index 931c22f7a7..0df586aaf0 100644
--- a/src/ol/geom/multipolygon.js
+++ b/src/ol/geom/multipolygon.js
@@ -150,7 +150,7 @@ ol.geom.MultiPolygon.prototype.containsXY = function(x, y) {
 
 
 /**
- * @return {number} Area.
+ * @return {number} Area (on projected plane).
  * @api
  */
 ol.geom.MultiPolygon.prototype.getArea = function() {
diff --git a/src/ol/geom/polygon.js b/src/ol/geom/polygon.js
index 1647763055..9b38853418 100644
--- a/src/ol/geom/polygon.js
+++ b/src/ol/geom/polygon.js
@@ -140,7 +140,7 @@ ol.geom.Polygon.prototype.containsXY = function(x, y) {
 
 
 /**
- * @return {number} Area.
+ * @return {number} Area (on projected plane).
  * @api
  */
 ol.geom.Polygon.prototype.getArea = function() {