First you need to measure the circumference around your cock from behind the balls. You can use a fabric tape measure (the kind dressmakers use) to get the measurement, or, if you don’t have one, you can use a piece of string and a ruler.Wrap the tape measure or string around your cock, going behind the balls. The tape should be snug but not tight. The last thing you want is to suffer from circulation problems, so a good time to take this measurement is after a shower or bath when your body is most likely at it’s warmest. 

Now you have your circumference you need to divide it by 3.14 to get the diameter. We’ve done some sample calculations below to show you how it works: 

Firstly in metric:17.3 cm ÷ 3.14 = 55mm diameter 

15.7 cm ÷ 3.14 = 50mm diameter 

14.1 cm ÷ 3.14 = 45mm diameter 

12.5 cm ÷ 3.14 = 40mm diameter 

And in imperial:7 inches ÷ 3.14 = 2.25 inches diameter 

6.25 inches ÷ 3.14 = 2 inches diameter

5.5 inches ÷ 3.14 = 1.75 inches diameter 

4.7 inches ÷ 3.14 = 1.5 inches diameter