diff --git a/css-values-3/Overview.bs b/css-values-3/Overview.bs
index f34559d199e6..c135c112d533 100644
--- a/css-values-3/Overview.bs
+++ b/css-values-3/Overview.bs
@@ -1005,7 +1005,9 @@ Relative Lengths</h3>
 		<tr><td>''vw''
 			<td>1% of viewport's width
 		<tr><td>''vh''
-			<td>1% of viewport's height
+			<td>1% of viewport's height when user agent chrome is minimized
+		<tr><td>''vhc''
+			<td>1% of viewport's height when user agent chrome is maximized
 		<tr><td>''vmin''
 			<td>1% of viewport's smaller dimension
 		<tr><td>''vmax''
@@ -1178,7 +1180,13 @@ Viewport-percentage Lengths: the ''vw'', ''vh'', ''vmin'', ''vmax'' units</h4>
 
 		<dt><dfn id="vh" lt="vh">vh unit</dfn>
 		<dd>
-			Equal to 1% of the height of the initial containing block.
+			When user agent chrome does not change size, it is equal to 1% of the height of the initial containing block.
+			When user agent chrome does change size, it is equal to 1% of the height of the initial containing block with the user agent chrome at its smallest size.
+			
+		<dt><dfn id="vhc" lt="vhc">vhc unit</dfn>
+		<dd>
+			When user agent chrome does not change size, it is equal to 1% of the height of the initial containing block.
+			When user agent chrome does change size, it is equal to 1% of the height of the initial containing block with the user agent chrome at its largest size.
 
 		<dt><dfn id="vmin" lt="vmin">vmin unit</dfn>
 		<dd>
@@ -1188,6 +1196,10 @@ Viewport-percentage Lengths: the ''vw'', ''vh'', ''vmin'', ''vmax'' units</h4>
 		<dd>
 			Equal to the larger of ''vw'' or ''vh''.
 	</dl>
+	
+	Note: The vh and vhc units are the same size when the user agent chrome does not change size
+	(for example, desktop user agents generally do not change chrome size, so vh and vhc will be the same in these situations).
+	For user agent whose chrome does change size, vhc is the smaller of the two units.
 
 	<wpt>
 	css/css-regions/interactivity/resizing/regions-resizing-003.html