Ring Blank Calculator

The inner circumference alone would only fit snugly on the inside edge of the band. When a flat strip bends into a ring, the outside edge has to travel farther than the inside edge, so the strip's neutral bending line sits partway out from the inner circumference — roughly half the metal's thickness. This calculator adds π times the Metal Thickness to the inner circumference to account for that extra length, then adds a fixed 1.5mm overlap so the two ends of the strip have material to solder together instead of meeting edge to edge with nothing to fuse.

This calculator uses a standard linear approximation that tracks published ring-size-to-circumference charts closely enough for bench fabrication, generally within well under a millimeter across the 1-16 size range. Small differences between charts exist because US ring sizes are a rounded, standardized convention layered on top of a continuous circumference measurement, so different reference sources round slightly differently. For a critical commission, verify the target circumference against a ring sizer or mandrel you trust before cutting.

No — Band Width only sets Strip Width, the dimension of the strip running along the ring's height (front to back). Strip Length is governed entirely by Ring Size (which sets the circumference to be bent around) and Metal Thickness (which adds a small correction for the bending radius). You can widen or narrow the band without affecting how long a strip you need to cut for a given ring size.

Thicker metal has more distance between its inner and outer bent surfaces, so its neutral bending line — the layer that neither stretches nor compresses as you form the ring — sits farther out from the true inner circumference. This calculator adds π times the Metal Thickness to compensate, which is why increasing gauge from, say, 0.8mm to 1.5mm adds roughly 2mm of extra strip length even though the ring size hasn't changed.

It computes a theoretical cutting target from geometry alone. It does not account for saw kerf (material lost to the blade), filing and finishing losses, spring-back in harder alloys, or the specific calibration of your own ring mandrel, all of which can shift the real amount of stock you need by a millimeter or more. Cut slightly long on a first attempt with an unfamiliar metal or mandrel, and true up the final fit before soldering.