I came across an ISO, say ISO 12345:78, and wondered what is the way to pronunce it:

  • For the ISO part, should I say...

  • "ei" "es" "ou"?

  • or "aiso"?

  • For the 12345:78 part, should I say...

  • "one" "two" "three" "four" "five" "colon" "seven" "eight"?

  • or "twelve" "thirty-four" "five" "colon" "seventy-eigth"?

  • or "twelve thousands, three hundred fourty-five" "colon" "seventy-eigth"?

Also, for the ":" part, should I proununce "colon" or just say nothing?

I found a couple of interesting debates in wordreference, but it still a bit uncertain to me if there is a standard way of doing it:

  • 1
    I'm not a professional engineer, so I'm hestitant to give this as a proper answer. I've heard both "eye-ess-oh" and "aiso" for ISO. The numbers are usually read as as whole numbers rather than a series of digits, and I've never heard anyone say "colon." "Aiso twelve thousand three hundred forty five <pause> seventy eight." Nov 4, 2014 at 12:54
  • Thanks a lot, @JasonPatterson Feel free to post the comment as the beginning of an answer. You (I assume English native speaker) using it is a good reference for me.
    – fedorqui
    Nov 4, 2014 at 16:03
  • 1
    I have only heard aiso pronunciation in AmE. The numbers can be read different ways, but the colon should be replaced by "part, section, article, etc." depending on how those sections are indicated in the document.
    – user3169
    Nov 4, 2014 at 17:42
  • @user3169 thanks, that makes sense. Feel free to post an answer, this was useful!
    – fedorqui
    Nov 7, 2014 at 11:41
  • 1
    I've never heard "EYE-SO", always "EYE ESS OH". For the number, the first digits are usually, but not invariably, read as a digit sequence. Since (in my experience) the :N part has always been a year (the year that particular version of that particular standard was established), I read the colon as "OF" and the digits following as a year - so ISO 9001:2000 is "EYE ESS OH NINE THOUSAND ONE OF TWO THOUSAND", but ISO 12345:78 would be "EYE ESS OH ONE TWO THREE FOUR FIVE OF SEVENTY EIGHT". Oct 17 at 11:48

2 Answers 2


I have only heard aiso pronunciation in AmE.

The numbers can be read different ways, but instead of saying "colon" you should say "part, section, article, etc.", depending on how those sections are indicated in the document

  • 2
    I think that most people would pronounce ISO like "aye ess oh," but saying "aiso" wouldn't be unheard of. I am partial to "aiso" myself since it is how I refer to .iso formatted archive images. (I am also American.)
    – Crazy Eyes
    Nov 7, 2014 at 22:32
  • 5
    @CrazyEyes I guess there is no standard on how to say ISO...
    – user3169
    Nov 8, 2014 at 19:38
  • I personally have never heard aiso as an AmE college student Jun 22 at 22:28

It depends on the number, and is not really consistent. I'd say "iso nine thousand and one", but also "iso six thirty-nine", and "iso eight six oh one". Whatever seems clearest or more convenient in the moment.

For the sub-numbers I normally just pause. So "iso nine thousand and one, two thousand", or sometimes "iso six three nine part 2", but I don't think I've ever said "colon".

Note that "iso" is a word/prefix by itself. Your phonetic spellings are very non-standard,

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