Measuring for a Cock Ring:

1. Take a measuring tape and slip it behind your balls and tug it up around the top of your penis (where it meets your body). The tape should be pulled snugly to get an accurate measurement, but do not pull it too tight. Alternatively, you could use a string if you do not have a measuring tape on hand. 

2. This measurement will give you your circumference of your cock and balls (behind your scrotum). 

3. Take your circumference measurement and divide by 3.14 to give you your diameter.

4. Repeat a few times to get an accurate measurement. 

5. When choosing your ring, do not choose a diameter smaller than your actual measurement.

Measuring for a Glans Ring:

1. Take a measuring tape and slip it behind the head of your penis. The tape should be pulled snugly to get an accurate measurement, but do not pull it too tight. Alternatively, you could use a string if you do not have a measuring tape on hand. 

2. This measurement will give you your circumference.

3. Take your circumference measurement and divide by 3.14 to give you your diameter.

4. Repeat a few times to get an accurate measurement. 

5. When choosing your ring, do not choose a diameter smaller than your actual measurement.