diff --git a/speckle_connector_3/src/speckle_objects/geometry/arc.rb b/speckle_connector_3/src/speckle_objects/geometry/arc.rb
index 5cf0f5b..2509917 100644
--- a/speckle_connector_3/src/speckle_objects/geometry/arc.rb
+++ b/speckle_connector_3/src/speckle_objects/geometry/arc.rb
@@ -18,18 +18,19 @@ module SpeckleConnector3
           plane = arc['plane']
           units = arc['units']
           origin = Point.to_native(plane['origin']['x'], plane['origin']['y'], plane['origin']['z'], units)
+          start_point = Point.to_native(arc['startPoint']['x'], arc['startPoint']['y'], arc['startPoint']['z'], units)
+          end_point = Point.to_native(arc['endPoint']['x'], arc['endPoint']['y'], arc['endPoint']['z'], units)
           normal = Vector.to_native(plane['normal']['x'], plane['normal']['y'], plane['normal']['z'], units)
           x_axis = Vector.to_native(plane['xdir']['x'], plane['xdir']['y'], plane['xdir']['z'], units)
           radius = Geometry.length_to_native(arc['radius'], units)
-          start_angle = arc['startAngle']
-          end_angle = arc['endAngle']
 
-          # Normalize angles to range 0 to 2π
-          start_angle %= 2 * Math::PI
-          end_angle %= 2 * Math::PI
+          start_vector = Vector.to_native(start_point.x - origin.x, start_point.y - origin.y, start_point.z - origin.z, units)
+          end_vector = Vector.to_native(end_point.x - origin.x, end_point.y - origin.y, end_point.z - origin.z, units)
 
-          # Ensure start angle is less than end angle for proper drawing
-          if start_angle > end_angle
+          start_angle = Math.atan2(start_vector.cross(normal).dot(x_axis), start_vector.dot(x_axis))
+          end_angle = Math.atan2(end_vector.cross(normal).dot(x_axis), end_vector.dot(x_axis))
+
+          if end_angle < start_angle
             end_angle += 2 * Math::PI
           end