Segmented Turning Calculator

A segmented ring is just a regular polygon inscribed in a circle, so once you fix the outer diameter and how many segments will make up the ring, the rest of the cutting geometry follows directly. The miter angle — the angle each segment's edge is cut at — is 180 divided by the number of segments; a 12-segment ring, for instance, needs 15° miters. From there, the calculator computes the segment's outer edge length as 2 × outer radius × sin(miter angle), and its inner edge length the same way using the inner radius (outer radius minus your target ring width), since the inner and outer faces of a trapezoidal segment aren't the same length — the outer edge is always the longer one. It multiplies the outer edge length across all segments, adding your saw kerf as waste between each cut, to tell you how much linear board length one ring will consume, then scales that by however many identical rings you're stacking to get a running total.

Board width needed is simply the ring width plus a small 1/16-inch sanding allowance for cleanup after glue-up. Two things trip people up here: first, the "board length" figure assumes you're cutting segments end-to-end from a single board, not nesting them more efficiently across a wider board, so it's a conservative (safe) estimate, not a minimum. Second, the miter angle here is the saw blade angle for cutting the segment ends — it is not the sled or fence angle some saws label differently, so confirm which reference your particular jig uses before cutting a full ring's worth of segments.