there is no such thing as correct length - everybody is different
Normally 6 inches and above. Some Asians have less than 6 inches.
Whats your length, lt me tell you if I know your length I can tell more
if that is shorter. Tell me also your age.
the correct length is one that does the job for you personally! so long as you can pee from it and do anything else you choose comfortably then thats all there is to it