This page shows you how to take the two measurements retailers ask for, and — just as importantly — how much they can be wrong by. Nothing you measure is entered here, stored, or sent anywhere. There is no calculator on this page.
We captured product records from eight open retail sources and looked for listings that publish both key measurements as clearly labelled fields, tied to the specific variant you would receive.
We did not find any. Not a low share — none. Ring diameter alone appears often; cage length appears far less often; the combination, verifiable to one variant, did not appear at all.
We are deliberately not giving you a percentage here. We published disclosure rates before and withdrew all of them: three defensible definitions of “chastity device” gave us samples of 629, 448 and 273 records, a spread too wide for any share to mean much. The count of zero does not depend on which definition you pick, which is why it is the only figure left standing.
That means any tool claiming to convert your measurements into a specific model would be guessing. We would rather teach you to measure well and tell you what to ask a retailer than hand you a number with a confidence it has not earned.
Measure around the base of the shaft and testicles together, where a ring would sit. Use a soft tape or a strip of paper you mark and then measure flat. Divide the circumference by 3.14 to get the inside diameter.
Where this goes wrong: Measure at the same time of day, twice, on two different days. Bodies change size through the day and across a week — a single measurement is the most common source of a bad fit.
Measure from where the ring sits to the tip while fully flaccid, without pressing the tape into the skin.
Where this goes wrong: Retailers rarely state whether their number is external shell length or usable internal length. These are not the same, and the difference is often 5–15 mm. Treat any single published number as unverified until the retailer confirms which one it is.
Because published specifications are inconsistent, these questions do more for fit than any calculator:
Remove the device promptly **if it can be removed safely** when you notice new or worsening pain, progressive swelling, difficulty urinating, or marked change in skin colour. If the device is stuck, or cannot be removed without risking injury, seek urgent medical care rather than attempting a hazardous removal. Have a way to remove it available at all times.
On the state of the evidence: we did not find studies covering routine long-term wear. The published medical literature in this area is concentrated in emergency case reports of entrapment and strangulation injuries. Those describe what happens when something goes wrong; they are not evidence that ordinary long-term wear is safe, and we will not present them as if they were. If you have circulation, sensation, or skin conditions, talk to a clinician rather than relying on any guide, including this one.