Ring Diameter Calculator
Convert a hoop’s internal diameter and circumference, or find a comfortable internal diameter from a wearable measurement.
Get the hoop that sits right
The difference between a hoop that looks perfect and one that pinches or spins is usually a millimetre or two of internal diameter. Because rings are sized inside-out and listings mix diameter with circumference, a quick conversion saves ordering the wrong size — especially when you’re matching a new hoop to one you already like.
Match the wire thickness with the Gauge Size Converter, and if you’re stretching, size plugs and tunnels alongside the Gauge Stretching Planner.
Frequently Asked Questions
Is a ring measured by its inside or outside diameter?
Body-jewelry rings — captive bead rings, seamless hoops, clickers — are sized by their INTERNAL diameter, the gap inside the ring. That's what determines how it sits on the piercing. The tool works in internal diameter throughout, and converts to circumference (the distance around the inside) using plain circle geometry.
How does the diameter relate to circumference?
By the circle formula: circumference equals π times the diameter. A 10 mm internal-diameter ring has an inner circumference of about 31.4 mm. That's handy when a listing gives one figure and you want the other, or when you're comparing a hoop against a curved measurement.
What internal diameter should I choose for a placement?
It depends on the anatomy and the look you want — a septum or daith needs enough diameter to clear the tissue and sit comfortably, while a tight lobe hoop is smaller. The 'find a comfortable diameter' mode adds a small gap over the measurement the ring has to clear. Treat it as a starting point and let your piercer confirm what suits your placement.
Does this size the bar thickness too?
No — this handles diameter and fit only. The thickness of the ring wire is its gauge; convert that separately with the gauge size converter. A ring listing usually gives both, for example '16g 10mm', meaning a 1.2 mm-thick wire formed into a 10 mm internal-diameter hoop.
Sizing guidance only — your piercer can confirm the diameter that fits your placement. Not medical advice.