# Spaces between numbers and units

Ok, so I write this beautiful answer ;-), and then comes this hooligan insert spaces between all my numbers and units. 600V is not "600V", it's "600 V". I've seen edits like that before, but I wonder if that's necessary. Yes, I'm aware of ISO-31, but do we give a damn? I've posted 1115 answers so far and nobody ever complained that he couldn't read "600V". I think it's unnecessary, and it only bumps the question.
What do others think?

edit
Just posted an answer nicely inserting the spaces when I hit upon a problem. I write "4/20 MHz" and it looks like "(4/20) MHz" (200 kHz)or , while I mean "4/(20 MHz)", (200 ns). How do you read "4/20 MHz"?

• "but do we give a damn?" I do, but I'm more pedantic than most. Jun 11 '12 at 15:11
• @endolith - Normally me too, and I can drive colleagues crazy with standards. But not so much if it applies to me :-). Too stubborn I think. Jun 11 '12 at 16:06
• I read it 200 kHz :) To say that you can use real fractions or write 4/20M Hz^-1 Jun 12 '12 at 13:45
• @clabacchio - (commenting here, otherwise you won't get notified) Thanks for the edit of this answer. I didn't like the italics either, but I didn't know "mathrm". Thanks again. Jun 12 '12 at 16:24
• Your edit brings up a good point. This is one reason I violate the rule of space between value and units when in expressions with arithmetic operators. I surround the operators with spaces, but glue the value and units together. In your case, I would have written "4 / 20MHz". The spaces thing is a guide, not a hard rule that you go to jail for violating. Jun 12 '12 at 17:05
• @OlinLathrop and steven, with mathjax in the 4/20 can look much nicer, although relatively small in a comment. $\frac{4}{20}$ Jun 12 '12 at 17:16
• @Kortuk - Yes, $\frac{4}{20 \mbox{ } MHz}$ is definitely unambiguous, but I find it a bit too small to read, I usually use \dfrac, but on a separate line for equations. Inline $\dfrac{4}{20 \mbox{ } MHz}$ disrupts the text flow. I know, I'm difficult :-/ Jun 12 '12 at 17:22

As for your example, it was already fairly near the top, and the reason for the edit was primarily to remove dozens of single-character MathJax calls. They look ugly (they're italicized by default which clashes with the rest of the text), and are are slow.

More to your question, 600V isn't that bad, but 1µA, 1MΩ are worse. I'm not liable to bump a question to fix one or two, but if I stumble across a question which has several formatting issues, it's likely. Deciding whether or not to edit a post involves many factors, chief among which is the do-I-feel-like-it factor.

If you're asking my opinion about how posts should be written ("if I was king"), there should be a space between numbers and units as per the standard you site as well as NIST (see #10 on the checklist, or below) and SI. If it's in reference to some sort of nominal value (a 12-V car battery, 5-V logic), I think there is some other method for that but I am not sure.

NIST Special Publication 811 2008 Edition

# Guide for the Use of the International System of Units (SI)

## 7 Rules and Style Conventions for Expressing Values of Quantities

### 7.2 Space between numerical value and unit symbol

In the expression for the value of a quantity, the unit symbol is placed after the numerical value and a space is left between the numerical value and the unit symbol.

The only exceptions to this rule are for the unit symbols for degree, minute, and second for plane angle: °, ', and ", respectively (see Table 6), in which case no space is left between the numerical value and the unit symbol.

Example: α = 30°22'8"

Note: α is a quantity symbol for plane angle.

This rule means that:

1. The symbol °C for the degree Celsius is preceded by a space when one expresses the values of Celsius temperatures.
• Example: t = 30.2 °C but not: t = 30.2°C or t = 30.2° C
2. Even when the value of a quantity is used as an adjective, a space is left between the numerical value and the unit symbol. (This rule recognizes that unit symbols are not like ordinary words or abbreviations but are mathematical entities, and that the value of a quantity should be expressed in a way that is as independent of language as possible—sees Secs. 7.6 and 7.10.3.)
• Examples:
• a 1 m end gauge but not: a 1-m end gauge
• a 10 kΩ resistor but not: a 10-kΩ resistor

However, if there is any ambiguity, the words should be rearranged accordingly. For example, the statement “the samples were placed in 22 mL vials” should be replaced with the statement “the samples were placed in vials of volume 22 mL.”

Note: When unit names are spelled out, the normal rules of English apply. Thus, for example, “a roll of 35-millimeter film” is acceptable (see Sec. 7.6, note 3).

• Ah no, if 600V isn't bad then 1MΩ isn't either. We have to be consistent. What's the matter with 1MΩ, anyway? Jun 11 '12 at 7:01
• @stevenvh if you note, when I edited your post I was consistent. I'm trying to espouse a pragmatic view than legislate absolutely. Jun 11 '12 at 7:05
• @stevenvh, I did not realize he had made a switch from mathjax to html, this actually does greatly increase the load time of a post, especially as you get to computers as old as olins. Jun 11 '12 at 7:05
• @Nick - I didn't say you weren't consistent in the edit. But you seem to think different about 600V and 1MΩ, and I wonder why? What's the difference? Jun 11 '12 at 7:07
• @stevenvh, the look of them to my eye is quite different, my eye can catch the 1 and the M with two matching vertical lines and reading it incorrectly is easier. Doing such with the V is nearly impossible next to the 0. Jun 11 '12 at 7:08
• @Kortuk - I can fix that by only using 12MΩ resistors ;-) Jun 11 '12 at 7:10
• @NickT, I agree it was an okay edit, as I have shared in my answer, but doing this in a large quantity is flooding the main page with edits that give no technical correction. No one doubts that there should be a space there by standard, but it is also nothing technical, improving one post on occasion is of value because you are also improving load time, but improving multiples in quick succession has the disadvantage of bumping to the front page. However no one agrees with my answer I will be the one that has to deal with it if something like this occurs and someone flags it. Jun 11 '12 at 12:55
• "flooding the main page with edits that give no technical correction" This is a problem with the site, not with making edits. Minor edits shouldn't bump a post to the main page or be awarded rep. Jun 11 '12 at 15:16
• @endolith, posts too minor to merit review should in general not happen, but in this case the user is improving load time. This is a messy boundary. Jun 11 '12 at 16:27
• @stevenvh For example this edit seems too minor to me also. Jun 11 '12 at 16:49
• @Kortuk - "RFID systems often work..." means 60% of them to me. "most RFID systems work..." means 95%. The latter will be closer to the truth. Jun 12 '12 at 15:59
• @stevenvh, yes, you did correct a minor difference in wording. If they wanted to specify they should have used a number. I do not care that you made the edit but it is very similar to what you are having an issue with in this question. I think as long as this is not a large part of our front page it is not an issue. Dont stop performing edits, just accept we all do this. Jun 12 '12 at 16:00
• @Kortuk Sorry for the delayed response but your post should read 65 % and 95 % :-) Feb 16 '17 at 22:08

I see nothing wrong with any edit, and more than being pedantic about standards, I really feel the space improves readability.

It has been discussed that a checkbox like "This is a minor edit" might be helpful for such smallish cleanups - if you don't like the question to reappear at the top of the list.

Just one note: I would enjoy spaces to be edited into my answers, but (outside MathJax) please with a non-breaking space ("&nbsp;") instead of a plain space (" "), because a line break between the number and the unit certainly doesn't improve readability.

I would consider an edit to place a space between 600 and V a very minor edit. I would consider it too superficial an edit to be worth doing if that is all someone is editing. I would suggest against it but I am not sure someone trying to improve a post, which was technically done here, is something they can feel free to do.

Just suggest to users whom you see do this that they try to save edits for more egregious errors. This is not something that is in itself an issue when done occasionally. This is only a real issue if the edits are flooding the main page with edits.

Do try to remember, this is someone taking their time to try to improve the look of your post. You should take it as them considering your post so valuable that polishing up these minor things are worth it. No one would do that for a poorly explained post. Take this as a compliment, not as someone voting down your post(wait, not a vote down).

• Thanks once more for the flowers! :-) I'll keep that in mind, but "improving the look" is very subjective. What an improvement is for one is a disgrace for someone else. Jun 11 '12 at 7:05
• @stevenvh, The proper formatting is supposed to have a space to my knowledge. We had someone get in an argument about this previously, it is the posters right to choose if they want to format it non-standard. You can always roll the post back, but if you decide to undo the spaces the post load time will be improved if you take the time to remove the spaces by hand and not use the rollback feature and return to mathjax. Jun 11 '12 at 7:07
• Yes, ISO 31-0 says there should be a space. Since ISO only sells documents I added a link to the wikipedia page. Jun 11 '12 at 7:12
• @stevenvh, yes, and again, it might be nitpicking, but it sounds like he was also removing the mathjax and the sapce was a side affect, again, trying to make a more substantial improvement then it may have seamed. Still somewhat minor in my eyes but if it is one post a day or less being edited this way, who cares. Really, as long as I dont see the front page flooded with edits like this then I am okay. Actually, thinking about it, if the front page was flooded with your posts that were detailed answering questions it might be better then the current ones on the front page for recruiting. Jun 11 '12 at 7:15

I totally agree - it is unnecessary. I have just had a look through 20 - 30 datasheets from 12 manufacturers and in the majority of cases, they don't put spaces between numbers and units.

The results of my (highly unscientific) "statistical analysis" show that whilst Bourns consistently uses spaces, Microchip uses spaces around 50% of the time and most others use spaces from zero to around 20% of the time - in the same datasheet!. I would also note that I had never even noticed this before in 30 years in the industry.

So I would suggest that we all have to be able to read values written without spaces ... and one users idea of improving the look of a post will not necessarily extend to all users.

Note to steven - You recently changed the spelling of "modelling" in one of my answers to "modeling". Since I speak EN-GB and not EN-US, I seriously considered changing it back!. In the end I re-worded the entire answer anyway. Just sayin' ;)

• The spelling checker on my Firefox is US, I'd love to swap it for a UK version, but the only one available seems to have a very limited dictionary, and is not stable. About modelling and modeling, the checker seems to like both :-). One word I keep having troubles with is canceled (also both with single "l" and double "ll" accepted. I try to remember how it shows on the displays at the airport :-). Before the internet I was chatting with an American on a BBS, and he said he thought I was English, but he couldn't understand why I would use American words! Haha! Jun 11 '12 at 15:39
• @stevenvh, I have been significantly let down by FF spell check, chrome on my work computer does much better then my FF at home for spell checking. Jun 11 '12 at 15:55
• @stevenvh - Actually, your English is way better than some native English speakers here I could mention! Jun 11 '12 at 15:56
• @Mike - Gee, thanks. I know my English is good. Much better than some of my other languages :-( (5 in total). Jun 11 '12 at 15:57
• @Kortuk - Maybe (or perhaps) I should have a look at Chrome. I love Firefox for its plugins (some 20 installed), but with the latest versions some of them don't work anymore, like the Googlebar! I can't do without my Googlebar! Jun 11 '12 at 16:00
• @stevenvh, Yes, I was hesitant also but changed because of some advantages with desktop notifications. Get a popup when someone pings me in chat just by having one tab to the side open to chat. Jun 11 '12 at 16:04
• @MikeJ-UK back to your post; are you saying editing posts soley to fix spaces is "unnecessary" or the spaces themselves are? I agree with the former; but if an edit is happening anyways, might as well fix the units. Jun 11 '12 at 16:08
• @Nick T - I am saying that considering common usage (eg manufacturers' literature) and the fact that I hadn't noticed the variations in style up until now, I don't even consider it a "fix" as such. Yes I am aware of the standards, but some of these have been written by people with too much time on their hands. Jun 12 '12 at 8:01