Sizing for cock rings
When sizing for a penis ring, it’s different from all other male sex toys, mostly because you need to measure the base of the penis where the penis ring will be sitting. As these are tight and restrict blood flow, the measurement you have might appear too large.
Because you are measuring right at the base of the shaft, it may be easier to ask a partner to help. It also helps to have no pubic hair because it really is advisable to be cleanly shaven when using a cock ring, otherwise rubbing or chafing can occur during use.
Make sure you have a good, solid erection before taking the measurements. Once you have this, gently wrap the cord or measure around the base of the penis. This is the circumference of your hard penis. A lot of manufacturers use diameter, so you can easily calculate this by dividing your result by 3.14.
Now you have both, you can quickly check both sizes against the cock rings. One thing to note is: it is the inner diameter of the toy that you will need.
Cock rings come in all sizes and range from inner diameters of around 0.75 of an inch, 0.9 of an inch and 1 inch. These stretch, so if you are unsure just order the next size up.