diff --git a/ui/less/ad_controls.less b/ui/less/ad_controls.less
index 73e5b65db4..92e6259916 100644
--- a/ui/less/ad_controls.less
+++ b/ui/less/ad_controls.less
@@ -82,7 +82,7 @@
    * That divided by 2 is margin on one side, so we take that, and move the
    * button from its normal position to the right by that percentage.
    */
-  right: (100 - @bottom-controls-width) / 2 * -1;
+  right: calc((100 - @bottom-controls-width) / 2 * -1);
   display: flex;
   flex-direction: row;
   margin: 0;
diff --git a/ui/less/buttons.less b/ui/less/buttons.less
index 6bbe896c50..fe9682df9e 100644
--- a/ui/less/buttons.less
+++ b/ui/less/buttons.less
@@ -26,7 +26,7 @@
    *
    * Based on tips from https://stackoverflow.com/a/12925343 */
   box-sizing: border-box;
-  padding: @play-button-size-percentage / 2;
+  padding: calc(@play-button-size-percentage / 2);
   width: 0;
   height: 0;
 
diff --git a/ui/less/containers.less b/ui/less/containers.less
index 7783dbc860..b4176195bf 100644
--- a/ui/less/containers.less
+++ b/ui/less/containers.less
@@ -263,8 +263,8 @@
 
 .shaka-spinner {
   /* This uses the same trickery as the big play button define
-  the spinner's width and height. See .shaka-play-button
-  for the detailed explanation. */
+   * the spinner's width and height. See .shaka-play-button
+   * for the detailed explanation. */
 
   /* For the padding thing to work, spinner div needs to be an
   overlay-parent and spinner svg - an overlay child. */
@@ -272,11 +272,11 @@
 
   margin: 0;
   box-sizing: border-box;
-  padding: @spinner-size-percentage / 2;
+  padding: calc(@spinner-size-percentage / 2);
   width: 0;
   height: 0;
 
   /* Add a bit of a white shadow to keep our black spinner visible
-  on a black background. */
+   * on a black background. */
   filter: drop-shadow(0 0 2px rgba(255 255 255 / 50%));
 }
diff --git a/ui/less/range_elements.less b/ui/less/range_elements.less
index 903f4caf7b..15efeae529 100644
--- a/ui/less/range_elements.less
+++ b/ui/less/range_elements.less
@@ -39,7 +39,7 @@
   .overlay-parent();
 
   /* Vertical margins to occupy the same space as the thumb. */
-  margin: (@thumb-size - @track-height)/2 6px;
+  margin: calc((@thumb-size - @track-height) / 2) 6px;
 
   /* Smaller height to contain the background for the virtual track. */
   height: @track-height;
@@ -109,7 +109,7 @@
 
   /* Position the top of the range element so that it is centered on the
    * container. Note that the container is actually smaller than the thumb. */
-  top: (@track-height - @thumb-size) / 2;
+  top: calc((@track-height - @thumb-size) / 2);
 
   /* Make sure clicking at the very top of the bar still takes effect and is not
    * confused with clicking the video to play/pause it. */