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In everyday language, people call "1/100" 1 percent. How do I say "1⁄1000"?

O point one percent

1 thousandth

or something else?

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  • In finance this could also be called "10 basis points"
    – D Stanley
    May 22, 2020 at 19:37
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    Worthy of note: if you're talking about 1/1000 of some metric measurement (e.g. meters, seconds, joules, newtons, grams, liters, amps, volts, ...), you can use the milli- prefix (e.g. millimeter, millisecond) - or whatever metric prefix is appropriate. This is very common in scientific practice since "three millimeters" is a lot easier and clearer than "three thousandths of a meter."
    – Milo Brandt
    May 23, 2020 at 3:27
  • Every time I've read the title to myself I've said over... but putting people at the end I immediately switched to out of. - Context is king. Same with, "if you're talking about 1/1000 of some[thing]" (which I read as one one-thousandth of something... that's three different ways you can say "1/1000", all depending on the word that comes after it)
    – Mazura
    May 23, 2020 at 19:52
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    IMHO, if it's written as "1/1000", you should not pronounce as "0.1%". If a book writes "machete", you would not pronounce that as "knife".
    – Thomas Weller
    May 25, 2020 at 6:35

9 Answers 9

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Either of the ways that you show, but if you are spelling them as they are said, this is consistent:

"zero point one percent" (written 0.1%)

"one thousandth". (written 1/1000 or 0.001)

You can also say "one part per thousand" (1 PPT).

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  • 35
    There's also a dedicated but rarely-used symbol for this called per mille: ‰.
    – TypeIA
    May 22, 2020 at 6:33
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    Also, One tenth of one percent or One tenth of a percent.
    – AbraCadaver
    May 22, 2020 at 14:51
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    @Panzercrisis As far as I can see, no problem arises for "one thousandth" on its own (or even "a thousandth"). The convention that I use for interpreting the phrase "two thousandths" standing alone would be as 2/1000. There is no contradiction, nor ambiguity introduced when interpreting e.g. "five two thousandths" as 5/2000 and "a two thousandth" as 1/2000. It doesn't matter that one number can be read out several ways - that occurs anyway as soon as we have fractions. (However, this is the Internet, so someone will probably butt in with "But my teacher always said..." any second now.)
    – Robert Furber
    May 22, 2020 at 18:14
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    Although both forms are acceptable, there is a subtle idiomatic difference between "one thousandth", and "one one-thousandth". English speakers would be inclined to use the latter form if they are emphasizing that the value is small.
    – Robin Davies
    May 23, 2020 at 8:14
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    @TypeIA it's not that uncommon, at least in other countries. In Sweden, the blood alcohol level (of a driver) is usually expressed in "promille" ‰, including in the official text of the law. lagen.nu/1951:649 (Swedish)
    – MEMark
    May 24, 2020 at 12:03
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If you want a term similar to percent, but ten times smaller, it's per mille, denoted by ‰ sign. So, 0.1%=1‰.

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    You will commonly see this used for property taxes (at least in the US), where they give the "millage rate".
    – eps
    May 22, 2020 at 12:48
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This question is part math, part language and part pronunciation. You can say (pronounce) any of the following, because they are mathematically the same:

  • A thousandth
  • One one-thousandth
  • One out of a thousand
  • .1 percent ("point one percent" or "one one-tenth of a percent")
  • per thousand or one per thousand

As mentioned in comments, there is use of "per mill" (also spelled 'mil') in the same fashion as 'per cent.' 'Mill' is used for "one-thousandth" in specific financial contexts, including taxation rates. A tax rate in mills (or a "millage" rate) of 3 means three dollars per 1,000 dollars of value, for example. (Related to prefix milli' for thousanths, derived from French 'mille' meaning 'one thousand')

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  • Per mille is used in American English, it's just quite rare. It mostly shows up in finance and engineering.
    – Hearth
    May 22, 2020 at 16:00
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    This is a good answer, but I can't upvote because the math is wrong
    – BlueRaja - Danny Pflughoeft
    May 22, 2020 at 17:24
  • @Blue, where is the math wrong?
    – Mazura
    May 22, 2020 at 21:50
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    @Mazura 1/1000 is 0.1%, not 0.01%
    – BlueRaja - Danny Pflughoeft
    May 22, 2020 at 22:06
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    Per mille is also written as per mil. A mil is also one thousandth of an inch when measuring length, and one tenth of a penny when counting money. Printed savings coupons may have a note saying they have a cash value of one tenth of a mil, or half a mil, etc. This originated with the old practice of trading stamps (S&H Green Stamps were one popular type.)
    – barbecue
    May 23, 2020 at 15:23
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"1/100" is not one percent. It's, one over one hundred.

"1⁄1000" is, one over one thousand.

Your question is, how do you say ".001" and your second offering is correct : one thousandth. You can also say, point zero zero one.

"0.1%" you can omit the zero and just say, point one percent.

You can't say "one part per thousand" because we don't have the context of there being "parts".

Mathematical formulas can be vocalized (spoken aloud). The vocalization system for formulas has to be learned, and is dependent on the underlying natural language. For example, when using English, the expression "ƒ(x)" is conventionally pronounced "eff of eks", where the insertion of the preposition "of" is not suggested by the notation per se. The expression " d y d x {\displaystyle {\tfrac {dy}{dx}}} \tfrac{dy}{dx}", on the other hand, is commonly vocalized like "dee-why-dee-eks", with complete omission of the fraction bar, in other contexts often pronounced "over". The book title Why does E = mc2? is said aloud as Why does ee equal em see-squared?.

– Language of mathematics

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    "1/100" is one percent, and anyone who graduated elementary school would understand if you read it as such. Additionally, OP never gave context, so it may be perfectly fine to say "one part per thousand". Unless the context is mathematical, I would discourage anyone from using "one over one thousand". "One out of a thousand" would be preferable for statistics.
    – Micah Windsor
    May 22, 2020 at 14:27
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    @MicahWindsor - Why would you discourage anyone from using "one over one thousand" ? Oh, "Unless the context is mathematical" .... it's numbers (with an operator in between them), how is it not mathematical?
    – Mazura
    May 22, 2020 at 14:49
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    I said I would discourage them from saying that unless the context is mathematical. The reason is because it is essentially a description of how it is written in fraction form, i.e. one number over the other. If it is a statistic and has relevance to a real world situation, it's better to use something that makes this fact obvious. It's like how math teachers always tell students off for not giving units with a number. 1 is just a number. 1 person is a tangible thing.
    – Micah Windsor
    May 22, 2020 at 14:54
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    But would you say, "One over a thousand people are born with X condition"? Or would you say "0.1% of/one out of one thousand people are born..."? That was my point. If I was to vocalize the equation "1/1000=2^x", I would say "One over one thousand equals two to the x", however.
    – Micah Windsor
    May 22, 2020 at 22:33
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    @MicahWindsor - I'd say one out of ; a ratio. But the question is, How do I say [this fraction]. Not, 'How do I say "1⁄1000" people...' (every time I've read the title to myself I've said over... but putting people at the end I immediately switched to out of). - Context is king, and here we are pilgrims in a lawless land. The only time the OP said people was when they were putting words in my mouth, an "everyday" speaker of English.
    – Mazura
    May 22, 2020 at 22:44
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That's a thousandth of something.

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As a fraction, other answers have cover that well.

When one want to express “1⁄1000” like some percentage, one could say as below and even write using a single Unicode character.

Write as 0.1% and say "one tenth (of a) percent".
(Below are useful in select conversations - uncommon in general)
Write as 1‰ and say "one per mille".
Write as 10‱ and say "ten per ten thousand".

Hmmm, too much like @Ruslan good answer. Making it wiki.

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  • "1/1000" of WHAT? A percentage? Then for the love of god don't use a fraction.
    – Mazura
    May 23, 2020 at 22:21
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An informal way to say it is "One in a thousand". This kind of speech implies that it is either an estimate or intended as an exaggeration.

For a more exact number like 42/1000, "fourty-two out of a thousand" might be interpreted by the listener to be less precise than "fourty-two one-thousandths".

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Speaking, I would say 'a thousandth' or 'a tenth of a percent'. Using 'a' rather than 'one' in saying it seems nicer. Further, in exposition, 'a' is an indefinite article, which indicates the speaker does not know the identity of the noun, in this case the thousandth in particular. If you were speaking of a particular thousandth, perhaps the weight of sand which broke the camel's back then we would want to indicate we know that particular unit by using the definite article 'the' to say 'the thousandth pound of sand that broke the camel's back'.

Finally, if the unit of measure is the inch, a thousandth may be referred to as 'a thou' or 'a mil'.

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One mill also works; it is frequently used in discussions of real estate taxes in the U.S.

It is derived from “mille,” Latin for one thousand.

Until about 1970, M after a number meant “approximately one thousand.”

So 230M meant “close to 230 thousand.”

Then the jargon of the computer people became popular. For them, a K was 1,024, which made total sense in the binary world of computers, where 1024 = 2 to the tenth power and very closely approximated 1000.So suddenly, K became an abbreviation for 1000 and M becamean abbreviation for million.

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