diff --git a/libs/kimath/include/geometry/geometry_utils.h b/libs/kimath/include/geometry/geometry_utils.h
index 47679bb2b6..6aa5ecb529 100644
--- a/libs/kimath/include/geometry/geometry_utils.h
+++ b/libs/kimath/include/geometry/geometry_utils.h
@@ -2,7 +2,7 @@
  * This program source code file is part of KiCad, a free EDA CAD application.
  *
  * Copyright (C) 2018 Jean-Pierre Charras, jp.charras at wanadoo.fr
- * Copyright (C) 1992-2020 KiCad Developers, see AUTHORS.txt for contributors.
+ * Copyright (C) 1992-2021 KiCad Developers, see AUTHORS.txt for contributors.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
@@ -54,6 +54,13 @@ enum ERROR_LOC { ERROR_OUTSIDE, ERROR_INSIDE };
  */
 int GetArcToSegmentCount( int aRadius, int aErrorMax, double aArcAngleDegree );
 
+/**
+ * @return the max error when approximating a circle by segments
+ * @param aRadius is the radius of the circle
+ * @param aSegCount is the seg count to approximate the circle
+ */
+int GetCircleToSegmentError( int aRadius, int aSegCount );
+
 /**
  * When creating polygons to create a clearance polygonal area, the polygon must
  * be same or bigger than the original shape.
diff --git a/libs/kimath/src/geometry/geometry_utils.cpp b/libs/kimath/src/geometry/geometry_utils.cpp
index bfd8090707..a9d426b373 100644
--- a/libs/kimath/src/geometry/geometry_utils.cpp
+++ b/libs/kimath/src/geometry/geometry_utils.cpp
@@ -2,7 +2,7 @@
  * This program source code file is part of KiCad, a free EDA CAD application.
  *
  * Copyright (C) 2018 Jean-Pierre Charras, jp.charras at wanadoo.fr
- * Copyright (C) 1992-2019 KiCad Developers, see AUTHORS.txt for contributors.
+ * Copyright (C) 1992-2021 KiCad Developers, see AUTHORS.txt for contributors.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
@@ -63,6 +63,19 @@ int GetArcToSegmentCount( int aRadius, int aErrorMax, double aArcAngleDegree )
     return std::max( segCount, 2 );
 }
 
+
+int GetCircleToSegmentError( int aRadius, int aSegCount )
+{
+    // avoid divide-by-zero, and the minimal seg count used here = 2
+    // (giving error = aRadius)
+    aSegCount = std::max( 2, aSegCount );
+
+    double alpha = M_PI / aSegCount;
+    double error = aRadius * ( 1.0 - cos( alpha) );
+
+    return error;
+}
+
 // When creating polygons to create a clearance polygonal area, the polygon must
 // be same or bigger than the original shape.
 // Polygons are bigger if the original shape has arcs (round rectangles, ovals,
diff --git a/pcbnew/pcb_painter.cpp b/pcbnew/pcb_painter.cpp
index 2277bc9a37..98b96ccbef 100644
--- a/pcbnew/pcb_painter.cpp
+++ b/pcbnew/pcb_painter.cpp
@@ -703,11 +703,13 @@ void PCB_PAINTER::draw( const PCB_ARC* aArc, int aLayer )
 
 // Debug only: enable this code only to test the TransformArcToPolygon function
 // and display the polygon outline created by it.
+// arcs on F_Cu are approximated with ERROR_INSIDE, others with ERROR_OUTSIDE
 #if 0
     SHAPE_POLY_SET cornerBuffer;
-    int errorloc = aArc->GetBoard()->GetDesignSettings().m_MaxError;
+    int error_value = aArc->GetBoard()->GetDesignSettings().m_MaxError;
+    ERROR_LOC errorloc = aLayer == F_Cu ? ERROR_LOC::ERROR_INSIDE : ERROR_LOC::ERROR_OUTSIDE;
     TransformArcToPolygon( cornerBuffer, aArc->GetStart(), aArc->GetMid(),
-                           aArc->GetEnd(), width, errorloc, ERROR_LOC::ERROR_OUTSIDE );
+                           aArc->GetEnd(), width, error_value, errorloc );
     m_gal->SetLineWidth( m_pcbSettings.m_outlineWidth );
     m_gal->SetIsFill( false );
     m_gal->SetIsStroke( true );