The　roundness　error　for　minimum　circumscribed　circle　(MCC)　and　maximum　inscribed　circle　(MIC)　from　coordinate　data　is　obtained　according　to　the　distance　between　the　two　parallel　lines.　The　lines　for　MCC　and　MIC　can　be　found　based　on　convex　hull　and　polar　coordinates　and　be　determined　by　four　critical　measured　points　that　lead　to　an　efficient　way　to　solve　the　roundness　error.　In　this　paper,　an　approach　for　constructing　a　convex　hull　is　presented　using　vector　product.　The　method　developed　is　implemented　and　validated　with　the　data　available　in　the　literature.　(C)　2007　Elsevier　Ltd.　All　rights　reserved.