I often get confused when referring to gun sizes. I often say "caliper" when the term used is "caliber". Looking at the defintions, it seems to make no sense as "caliber" has two very different meanings; "caliper" also has two very distinct meanings.


  1. the quality of someone's character or the level of someone's ability.

  2. a) the internal diameter or bore of a gun barrel. b) the diameter of a bullet, shell, or rocket. c) the diameter of a circular body, such as a tube, blood vessel, or fiber.


  1. an instrument for measuring external or internal dimensions

  2. having two hinged legs resembling a pair of compasses and in-turned or out-turned points.

I think the confusion comes in the because when talking about "the internal diameter or bore of a gun barrel" one would think a term referring to a "instrument for measuring internal dimensions" would be more closely related than a word whose main meaning is "quality of character".

Is there a reason why "caliber" was chosen over "caliper"?

They are only one letter apart, so did they have a similar origin that eventually became more divided?

  • You are asking a question that reads very familiar. :-)
    – user140086
    Commented Jul 16, 2016 at 13:48
  • 1
    A diverging view from Arabic qalib found on web: "I suggest -- though I wouldn't bet my life on it -- that caliber actually comes from the Latin word Calibe meaning steel. Here for example is Bartholomaeus Anglicus in his Latin book De proprietatibus rerum, written in 1240 and quoted here as it was printed in 1483: nec calibe, nec ferro, nec etiam ferra, which translates as not steel, not iron, not other ferrous material. The book was one of the most popular and widely read books in late medieval Europe".
    – Graffito
    Commented Jul 16, 2016 at 18:42
  • Just for completeness, there is yet another use of caliber in reference to big guns. From Wikipedia Caliber - Referring to artillery, "caliber" is used to describe the barrel length as multiples of the bore diameter. A "5-inch 50 calibre" gun has a bore diameter of 5 in (12.7 cm) and a barrel length of 50 times 5 in = 250 in (6.35 m). The main guns of the USS Missouri (Iowa Class Battleship) are 16" 50 caliber.
    – Phil Sweet
    Commented Jul 17, 2016 at 0:33
  • One easy way to distinguish between them is to spell calibre in the <strike>correct</strike> BrE way. !-) Commented Jul 19, 2016 at 8:08
  • Oh I give up on that joke I'm now going to whine about having no strike through in comments. Commented Jul 19, 2016 at 8:12

2 Answers 2


The sense of "inside diameter" is probably from the the Arabic meaning of "mold for casting bullets":


  • 1560s, "degree of merit or importance," a figurative use from Middle French calibre (late 15c.), apparently ultimately from Arabic qalib "a mold for casting." Arabic also used the word in the sense "mold for casting bullets," which is the oldest literal meaning in English. Meaning "inside diameter of a gun barrel" is attested from 1580s. Barnhart remarks that Spanish calibre, Italian calibro "appear too late to act as intermediate forms" between the Arabic word and the French.


  • 1
    my google-fu is weak... :(
    – Skooba
    Commented Jul 16, 2016 at 13:27
  • so is "caliper" a sheer coincidence?
    – Fattie
    Commented Jul 16, 2016 at 16:53
  • 2
    @JoeBlow - etymonline.com/index.php?term=caliper (you are a big boy, help yourself)
    – user66974
    Commented Jul 16, 2016 at 17:11
  • sigh I actually clicked the link. the info there seems crap. it does not at all explain if it's just a version of the same word :/ oh well ..
    – Fattie
    Commented Jul 17, 2016 at 4:25

Caliber was originally used to mean a unit of weight for cannon shot. So, for example, you might have "12 pounds caliber". Much later it came to mean a bore size, but until about 1800 guns were always sized by the weight of the shot.

The analogy to human characteristics refers to weight, not size. So, someone or something of "high caliber" would be someone weighty or serious.

  • 3
    Do you have any corroborating references you can cite here?
    – Jim
    Commented Jul 16, 2016 at 17:27
  • 2
    Perfect. You should be able to find one of those and insert a quote with a link then. ELU answers should be authoritative with cited references. Otherwise someone might come along and see your answer, not realizing you are the Emma Dash of A History of Military Arms and think you are just expressing an unsupported theory or wild conjecture.
    – Jim
    Commented Jul 16, 2016 at 17:36
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    @SáT Of course i’m being sarcastic. But it’s been 5 hours and there’s still no easily added citations in this answer...
    – Jim
    Commented Jul 16, 2016 at 21:57
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    -1 for an answer with no reference from a user with enough rep to know the customs here. I believe your answer because I did a bit of research, but I should not have had to. I'll gladly retract the downvote if you add a convincing reference. Just notify me when you do.
    – ab2
    Commented Jul 17, 2016 at 0:31
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    @SáT - I don’t see anything emotionally charged. I added a bit of humor, yes, emotion. No. And i’m pretty sure I can feel the fourth Turtle down starting to shake.
    – Jim
    Commented Jul 17, 2016 at 15:45

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