9 millimeter is the caliber.
IMPROVING ANSWER: A "9mm" bullet is actually .355 or .356 of an inch in diameter. So the caliber is about .36, but nobody calls it that because it would be confusing. Everybody calls it a 9mm and if somebody asks you what "caliber" that pistol is, you can answer "It's a 9mm" without having to add or explain anything.
further improve: 9mm is the correct answer. you can find the caliber by measuring the diameter of the bullet. translate to millimeters or inches and that's the caliber. 9mm is a 9mm caliber not "around .36"
9mm IS the caliber. If you mean what is it equivalent to, it is approximately the same as a .38.
Glock is a brand. 9mm is a caliber size. So, there is no difference between a 9mm glock and a 9mm of another brand as far as caliber size.
9mm is roughly .35 caliber, .32 caliber is slightly smaller, 3 hundredths of an inch smaller, in diameter.
The 9mm Parabellum(9mmLuger) is .355 caliber.
Caliber refers to the diameter of the bullet the gun fires. The caliber of a 9mm is 9 millimeters. That is about .356 inches.
9mm
9x19mm, also known as 9mm Parabellum or 9mm Luger.
No! 9mm = .35 caliber - .354 caliber!
The .22 bullet is smaller than the 9mm in size, (about 6mm) and is lighter in weight.
Most are in .380 ACP caliber. Sometimes called 9mm Short in Europe (or 9mm Corto or 9mm Kurz) What is marked on yours?
9mm = .355 40 cal = .40
9mm Parabellum