Bowl Segment Calculator

This bowl segment calculator gives you the cut sizes for a ring of a segmented woodturning project, the sort of glued-up ring that stacks into a bowl, vase or platter. Segmented turning builds each layer from a set of identical trapezoid pieces mitred at both ends so they close into a full circle, and getting the numbers right before you reach the saw is what keeps the joints tight and the glue-up square. Enter the number of segments you want in the ring, the finished outside diameter of that ring, and the width of the board you are cutting from (the radial depth of the ring), and the calculator returns the miter angle to set on your saw or sled, the length of the long outer edge and short inner edge of each segment, and the total length of board the ring needs. The miter angle is simply 180 divided by the number of segments, so more segments means a shallower angle and a rounder ring with less to turn away. The edge lengths come from the ring diameters and that same angle. Woodturners use it to plan each ring of a stack, to work out how much timber a project will swallow, and to check a design before committing good wood to the saw. Add a few millimetres per segment for the saw kerf and for trimming, and cut a test ring in cheap stock if the design is new.

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Cut 12 segments with a 15° miter at each end. Each piece is 67.0 mm on the long (outer) edge and 50.9 mm on the short (inner) edge, forming a ring 250.0 mm across the outside.

Miter angle is 180 divided by the number of segments; edge lengths use the ring diameters and that angle. Add a few millimetres per segment for kerf and trimming. Turn the flats round after glue-up.