How do I pronounce "ratio 1:1"?

Should I pronounce it "ratio 1 to 1"?

  • 8
    By spell do you mean pronounce? – ShreevatsaR Oct 6 '10 at 8:30
  • If you say it in that order, 'ratio' followed by '1:1' you'd say "ratio of 1:1". – Mitch Apr 20 '11 at 16:32
  • It is worth adding that while in isolation 1:1 is read as "one to one", when appearing in an equation it is read as "1 is to 1". For example 1:1 = 2:2 is read as "one is to one as two is to two. – mama Feb 19 '19 at 1:57

In speech this is obviously always pronounced "ratio one to one."

In writing, it is a matter of style. Anything of a technical nature should always be written in the 1:1 form, but when writing prose, fiction or something informal, you should certainly consider writing it as it would be spoken:

"The mix was applied in a one-to-one ratio."

The use of hyphenation and words instead of numerals makes the sentence flowing and readable, and encourages the reader's eye to see this as a single, commonly-occurring term.

Note that for the purpose of clarity ratios should generally be stated in the same clause and the same order as the two sets being compared:

"Boys and girls were present in a ratio of 3:2."

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  • the hyphenation of "one-to-one" is used because it is a phrasal adjective, and not simply because it is easier on the eyes. – horatio Jun 7 '11 at 14:53
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    It's never pronounced "ratio one to one" – Matt E. Эллен Aug 1 '12 at 13:13
  • Numbers that add up to 100 are a special case, though, especially 50:50; they are often pronounced by just saying the numbers, ignoring the colon. This leads many people to mistakenly write "50/50" rather that "50:50". – Acccumulation Feb 15 '19 at 22:27
  • @Acccumulation There is no mistake in writing “50/50”. Ratios can be expressed as fractions as well. But the phrase fifty-fifty isn’t really a fraction at all, conceptually speaking – the actual ratio of fifty to fifty would be better expressed as 1:1, with which it is entirely equivalent. The end result of a fractional and a rational correspondence may be mathematically equivalent, but they serve different purposes in communication. – Janus Bahs Jacquet Feb 15 '19 at 23:46
  • @JanusBahsJacquet "Ratios can be expressed as fractions as well." Ratios and fractions are different mathematical objects. Furthermore, in the context of probability, fractions will be expected to represent probability, while ratios will be expected to represent odds. – Acccumulation Feb 15 '19 at 23:50

The pronunciation/spelling-out of "1:1" is "one to one" or "one-to-one." I just wanted to add that you wouldn't say "ratio one-to-one." You would either say "a ratio of one-to-one" or "a one-to-one ratio."

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You would pronounce it "a ratio of 1 to 1", but it's worth noting that there are sometimes exceptions.

In films and photography, for example, ratios such as 16:9 and 4:3 are often described as "16 by 9" and "four by three", respectively.

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Hmm, not sure how correct this is but I read a:b as "a is to b". And a:b::c:d as "a is to b as c is to d". Probably British English (else it's Indian :))

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  • 1
    "Is to" is commonly used in India. Not sure if it has British roots. – MediumOne Apr 5 '11 at 11:14
  • In that formulation, yes : reads "is to" and :: reads "as". This is common on standardized tests in the USA. – T.E.D. Jun 7 '11 at 13:30
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    The OP specifically says that they're talking about ratios. That pronunciation is for analogies. – Acccumulation Feb 15 '19 at 22:28

I am Indian and I say 1:1 "one to one" and a:b::c:d "a is to b as c is to d".

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In the United States, "one-to-one ratio" is preferred. A pronunciation of "ratio" is given at the following.


In addition, The American Heritage Dictionary shows both a two-syllable and three-syllable pronunciation for ratio.


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  • "best" in what sense? And what citations do you have? – Acccumulation Feb 15 '19 at 23:07
  • @PeterShor I’m pretty sure I’d say /ˈreɪʃoʊ/. I’ve never really thought about it, but the di- and trisyllabic variants both sound perfectly normal and unremarkable to me. I’m quite surprised ODO doesn’t even give the disyllabic pronunciation as a variant. The OED only gives it as an AmE variant, which I’m quite sure isn’t right. I’ve definitely heard Brits say /ˈrεɪʃəʊ/ as well. – Janus Bahs Jacquet Feb 15 '19 at 23:52
  • @Janus: there are lots of people who say /ˈreɪʃoʊ/, and I wouldn't call it wrong. Claiming that it is the only correct, and also the historically correct pronunciation was a little over the top, though. (The answer was edited since.) – Peter Shor Feb 16 '19 at 0:37
  • @PeterShor I misread your initial comment, then – I read it as incredulity at the existence of the disyllabic pronunciation and was puzzled. – Janus Bahs Jacquet Feb 16 '19 at 0:38

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