The right size is the difference between a cock ring that works and one that either cuts off circulation or does nothing. Fortunately, getting it right takes about three minutes and a piece of string.
Why Girth, Not Length
The ring sits around the circumference of your shaft. The relevant measurement is girth, how wide around, not how long. Length is irrelevant to how a ring fits or performs.
Measure the wrong thing (length), and your size selection means nothing. Measure girth correctly, and sizing becomes simple.
The 3-Step Measurement
You need: a flexible measuring tape (cloth tailor's tape), or a strip of paper and a ruler.
Step 1: Measure when fully erect. The ring needs to fit at your functional size. A soft measurement will give you an undersized result. Erect girth is consistently larger, and a ring that fits softly will be too loose hard.
Step 2: Wrap the measuring tape around the base of your shaft. Not behind the balls. Shaft only, at the base. Hold the tape snug against the skin without pulling it tight.
Step 3: Read the circumference in inches and match it to the chart.
| BullRing Size | Shaft Girth |
|---|---|
| X (Small) | 4" to 4.75" |
| Y (Medium) | 4.75" to 5.5" |
| Z (Large) | 5.5" to 6.25" |
| ZZ (Extra Large) | 6.25" to 7" |
That's it. The number you measured goes in the left column; the right column is your size.
Sizing for BigBull, our cock-and-ball ring? It's measured differently: around the base, behind both the shaft and the balls. Use the BigBull sizing guide for its chart.
When to Measure: Morning vs. Evening, the Timing Question
When you're fully erect. That's the only answer that matters.
Morning erections are valid. Arousal-based erections are valid. The state you measure in should be the same state the ring will be used in.
Erect girth doesn't vary much with time of day for most men, unlike soft size, which fluctuates with temperature, stress, and other factors. If you notice your erect girth varies meaningfully day to day, use the larger measurement to avoid a ring that's too tight on your larger days.
Common Measurement Mistakes
Measuring soft. The most common mistake. Soft girth can be 30 to 40% smaller than erect girth. A ring sized to a soft measurement will be loose at best, useless at worst.
Pulling the tape tight. You're measuring natural circumference, not compressing it. Snug contact with the skin, not tension.
Using a string without measuring it accurately. If you're using a paper strip or string: wrap it, mark where the end meets the wrap, lay it flat against a ruler. The measurement point is the mark, not an estimate.
Rounding Up vs. Down: The Borderline Rule
If your measurement is clearly inside a size range, stay in that range. If you're right at a boundary (e.g., exactly 4.75", the boundary between X and Y):
- Round up (Y in this example) if you're newer to rings, want to start comfortable, or tend to be on the sensitive side
- Round down (X in this example) if you want more compression and you're confident in your measurement
The Starter Pack eliminates this decision: all four sizes in one order, right fit confirmed on the first use.
How to Convert From a Round-Ring Size
If you've used a traditional circular cock ring and know the inner diameter (ID) that worked:
Shaft girth ≈ Inner diameter × π
Practical conversion table:
| Round ring inner diameter | Approximate shaft girth | Suggested BullRing size |
|---|---|---|
| 1.3" (33mm) | ~4.1" | X |
| 1.5" (38mm) | ~4.7" | X |
| 1.7" (43mm) | ~5.3" | Y |
| 1.9" (48mm) | ~6.0" | Z |
| 2.1" (53mm) | ~6.6" | ZZ |
Note that shaft-only placement means BullRing sits higher than a full-base ring. The application point is different, so this conversion is approximate. When in doubt, try adjacent sizes, which is why the Starter Pack exists.
BullRing Sizes Explained
X (Small, 4" to 4.75"): Fits a slimmer shaft profile. Tightest compression of the four sizes.
Y (Medium, 4.75" to 5.5"): The most common size. Most men's erect girth falls in this range.
Z (Large, 5.5" to 6.25"): Above-average girth. Second most commonly ordered size.
ZZ (Extra Large, 6.25" to 7"): For the upper end of the girth range. If you've found other rings too tight, start here.
Printable Template Download
Print this page at 100% scale (no "fit to page"). The ruler on the template is accurate at true size. Wrap the ruler strip around your shaft when erect, mark the overlap, and lay it flat to read your circumference.
Download the BullRing printable sizing template (PDF, print at 100%)
The template includes the full size chart, measurement instructions, and a ruler strip you can cut out and use instead of a tape measure.
What If You're Between Sizes?
Try the larger size first for your initial session. If it feels loose or applies less compression than expected, try the smaller size next session.
The Starter Pack gives you both options, and the others, in one box. This is by design: sizing anxiety is the number one reason men delay their first order or end up with the wrong ring.
Frequently Asked Questions
Can I measure in centimeters?
Yes. X = 10.2 to 12.1 cm, Y = 12.1 to 14.0 cm, Z = 14.0 to 15.9 cm, ZZ = 15.9 to 17.8 cm.
Does girth change significantly during an erection?
Yes. Erect girth is substantially larger than soft girth for most men. Always measure erect.
What size is most commonly ordered?
Y and Z are the most common sizes ordered. Most men's erect shaft girth falls in the 4.75" to 6.25" range.
Is the ZZ the largest you make?
Currently, yes. If your erect girth is over 7" and ZZ is too tight, contact BullRing support directly to discuss options.
How do I know if I have the right size when I'm wearing it?
Correct fit: snug, noticeable compression, comfortable for sustained wear. Too tight: immediate pinching or pain, numbness, discomfort that increases quickly. Too loose: minimal sensation of compression, the ring slides or rotates freely.
Find your BullRing size · Full sizing guide · How BullRing works · BigBull sizing guide
