diff --git a/calibration.html b/calibration.html
index 49f8852..32c36c0 100644
--- a/calibration.html
+++ b/calibration.html
@@ -561,7 +561,7 @@
                     <tr>
                         <th>Reference Diagram</th>
                         <th>Segment</th>
-                        <th>Retraction distance</th>
+                        <th>Retraction distance (mm)</th>
                         <th>Retraction speed</th>
                         <th>Extra restart distance</th>
                     </tr>