Workpieces　like　a　shaft　or　hole　make　contact　on　their　functional　boundaries　and　its　circularity　is　obtained　based　on　the　functional　boundaries　by　enveloping　features.　Data　for　evaluating　roundness　error　can　be　obtained　from　coordinate　measuring　machines.　A　technique　for　roundness　error　based　on　the　curvature　has　been　proposed　to　deal　with　coordinate　measurement　data.　The　computational　geometric　concepts　of　convex　hulls　are　used　to　reduce　the　computation.　The　method　developed　is　implemented　and　validated　with　the　data　available　in　the　literature.　(C)　2009　Elsevier　Ltd.　All　rights　reserved.