You really shouldn't "dock" or cut a dog's tail off. But as far as natural length goes, it depends on the breeds.
how long do you leave a doberman tail
When it is a DOG.
If you adopt a six-week old Boxer puppy with an undocked tail, there is no need to take it to the vet, it is to late to have the tail docked.
A Shorkie adults tail only gets cut when it is frightened. A puppy does not.
More info has to be given even for a guess.
At a similar age to when you had your coccyx severed.
for looks
3-4 mm tail
Yes, mine was born with a short tail
Three to four months. That's how long we leave it on our Arabians, other wise their tails can start to rot. (left one in for 6 months, took it off and half the tail was gone)
When they aren't looking
Gerbils' tails should be as long as the gerbil itself. If they don't, their balance will be disturbed.