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Inch vs. Inches

I’m editing a technical manual. The engineers I’m working with have regularly typed amounts which are under one as “.05 inches” or “.67 inches.”

I’ve been of the opinion that this is to be typed “.05 inch” and “.67 inch,” as the amounts are less than one, but I can’t find anything to support either opinion.

Please advise.

  • April 17, 2008
  • Posted by Rob
  • Filed in Misc

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IMHO, it all depends on the way you are doing the number... I would say "1/2 inch", but would probably say ".5 inches" or ".5 OF AN inch". Just maybe accepted use of language with no steadfast rule.

khastings April 18, 2008, 9:34am

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I agree with your thinking: 0.5 and 0.67 are less than 1, hence, I'd use the singular. To me, this sounds right.

AO April 18, 2008, 8:33pm

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The correct answer is 'inch.'

Due to the way we speak, many times the wrong answer sounds correct.

In this case remember that we make plural any quantity over one.
so, .99 inch, 1.0 inch and 1.01 inches.

elizabeth April 20, 2008, 12:06am

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You could always use the abbreviation "in."

I agree with you and Elizabet.

See the National Geographic Style Guide:

"If the amount is less than one, the unit of measurement is singular: .33 inch (not inches) a day. If the figure is a one-digit decimal, use a zero before the point: 0.3 inch a day."

Of course writing and speaking are two different things and I would not really consider it a mistake if someone were to say that something is "point-six-five inches long".

Nick-alias April 25, 2008, 1:53am

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And what about adjectives? A ruler can be twelve inches long, but that makes it a twelve inch ruler.

porsche April 25, 2008, 8:59am

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Actually, I believe that makes it a "twelve-inch ruler" with hyphenation. Twelve becomes an adjective rather than a quantity.

Bill April 29, 2008, 8:12am

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Eliszbet - please note that "Due to..." is incorrect. This should be "Owing to..."

Stickler April 30, 2008, 5:44am

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Stickler, please not that there is nothing wrong with "due to."

Merriam-Webster's Dictionary of English Usage page 375:
"There is no solid reason to avoid using due to."

John April 30, 2008, 6:49am

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Thanks, John. I didn't think so...

@Stickler, if you are a stickler and you address my use of an adverbial versus an adjectival (owing to and due to) at least be a stickler for spelling my name correctly.


Elizabet May 1, 2008, 1:47pm

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Thanks everyone for the help on this. We've resolved the issue to my satisfaction.

Much thanks also to "Nick-alias" for the National Geographic link.

Rob May 28, 2008, 2:48pm

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A. Inches are not subdivided as decimals, but as simple fractions. (That's why they're so accurate)

B. If something sounds wrong when you say it, then it is wrong, but maybe not for the reason you think. 0.5 inch is just as wrong as 0.5 inches AND "half an inch" (though this last is allowed as idiom). The only meaningful way of stating this measure is "half of an inch", hence "0.5 of an inch" which can probably be safely abbreviated to "0.5 in", horrible though the thought may be (see A above).

Alright, why?

We like the sound of 0.5 inches because "five" is plural. We're conditioned to use plurals with plural numbers from when we first start to speak, so in everyday speech it's very hard to overcome (and probably pointless to try). "0.5" is a means of expressing "five tenths" in mathematical notation. Five tenths are of course plural for tenths, but not for decimal fractions of one... however grammar does not legislate for number less than singular. For this reason alone, I was taught at school that "0.5 inches" was NOT WRONG, but might occasionally be pounced on by editors, and the only way to pass under the radar was to say "0.5 of an inch".

Please note that the above post is littered with traps. I'm sure I've got another cigar somewhere...

Tolken June 9, 2008, 8:06am

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Yeah, really. I used to feel comfortable with things like "0.5 inches" and then for whatever reason I started saying "0.5 inch." I guess it's kinda like how I started to like hot peppers at some point in my up-bringing. Just a change of taste/habit.

You probably finished editing your technical manual a long time ago. At any rate, my personal experience tells me that "0.5 inch" may or may not be more correct, but at least sounds more technical. Maybe that's just because I started saying it later in my life, so I mark "0.5 inches" as more child-like and "0.5 inch" as more mature.

Who knows.

AO June 27, 2008, 3:47pm

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note that, while the abbreviations for most units of measure do not end with a period, the correct abbreviation for "inch" does end with a period, so as not to be confused with the preposition "in".

pound - lb
kilogram - kg
centimeter - cm
inch - in.
hour - hr
second - s

note also that when using these abbreviations, there are no grammatical dilemmas regarding pluralization.

tstilwel July 20, 2008, 11:00pm

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//Tolken says:
June 9, 2008, 8:06am
A. Inches are not subdivided as decimals, but as simple fractions. (That's why they're so accurate)

how can fraction be accurate??? only if the value is exactly 1/2, 1/4 etc
there are some numbers that can not be expressed with fraction, but can be written as accurate as you want with decimal system.
For example square root of 2 cm (1.41421356....), can be written 14142 um and can be easily converted 141 mm, depending on accuracy one needs. How do you do that in inches?
also metric system allows you to do random mathematical operations with random numbers without any converting.

im not saying you can not be more accurate using inches, you can, but it's useless as it is limited to only few numbers.

Ursus June 1, 2011, 9:44am

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in our company, we have our own style guide. the only individual number that is treated as singular is exactly one, neither more nor less. hence it should be "0.5 inches." but you can also write it as "half of an inch."

ann-other November 28, 2011, 1:18pm

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To Tolken and Ursus,

Regarding fractions and decimal numbers, neither one is fundamentally more or less accurate than the other. Also, any number that can be represented by one can be represented by the other. Every single rational number, terminating or repeating, can be represented as a fraction.

Irrational numbers, non-terminating and non-repeating, cannot be represented by a fraction OR a decimal number with perfect accuracy. They can only be approximated by such, and since every decimal can be converted to a fraction, any decimal approximation would be no more or less accurate than the corresponding fraction. Besides, while there are certain common conventions, accuracy can really only be known if the tolerance is specified for either.

Next, there's nothing special about inches that require the use of fractions whose denominator is a power of two. You can use English units but still use the decimal system for them.

porsche April 9, 2012, 5:54pm

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I see this is an old thread, however I feel the need to introject being an engineer.

I expect the desire to pluralize stems from the fact that we are often working with multiple fractions at a time (eg 3/4), however we would be less inclined to want to pluralize 1/4. However the numerator is not the subject of this conversation, it is the unit of that number we are discussing. Strictly speaking I would also never encourage a student to pluralize any measurement as the unit is just that; one unit.

To elaborate 1/3 of two inches would actually be 2/3, which is clearly not the intention being communicated. I do agree with Ursus however, in any practical environment (and any guidelines) the deprecated sizes of late British royalty's body parts should no longer be used as units of measure in a competitive global environment.

Jason K. October 14, 2012, 8:32pm

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I have these plans for a.shooting board but the inches refer to .5 of nan inch and .75 of an inch ehich i do not understand ,please reply btw the plans came from canada if that helps pleasa reply

Nathaniel George March 6, 2014, 10:59pm

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@Nathaniel George,

.5 of an inch=1/2 (of) an inch and .75 of an inch=3/4 of an inch.

Jasper March 7, 2014, 2:01am

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Our company style guide says, "In situations where space is an issue, such as in charts or tables, abbreviations may be used: 16-in. screen. Always abbreviate inches as in., don't use 0." What the heck do they mean by "don't use 0." (zero) ?

Craig Nelson May 11, 2016, 12:42pm

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'0.5 inch or 0.5 inches' refers to 0.5 of an inch - inch being the base unit. A base unit is singular, so former is logically correct.

'0.67 inch' is another issue. inch is divided into fraction. 0.67 appears to be two-thirds of an inch. Again the singular inch prevails.

Engineer September 4, 2016, 6:33am

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I bought a rug whose height is 0.32 inches. Is that more or less then 1/2 inch?

Judy May 6, 2017, 11:00pm

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What is 1/12 of 3?

Holly Fake May 7, 2017, 10:33pm

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Yes     No