diff --git a/src/src/Rendering/Measure/OpenPolyAnnotationActor.cpp b/src/src/Rendering/Measure/OpenPolyAnnotationActor.cpp
index af7be06..3cc8631 100644
--- a/src/src/Rendering/Measure/OpenPolyAnnotationActor.cpp
+++ b/src/src/Rendering/Measure/OpenPolyAnnotationActor.cpp
@@ -196,7 +196,7 @@ void OpenPolyAnnotationActor::UpdatePerimeterAndAreaText()
             BaseDataPoints->GetPoint(i, p1);
             BaseDataPoints->GetPoint(i - 1, p2);
 
-            distance += vtkMath::Distance2BetweenPoints(p1, p2);
+            distance += std::sqrt(vtkMath::Distance2BetweenPoints(p1, p2));
         }
 
         if(!Closed)