# What does 'double spacing' mean?

I think I know the meanings of \baselineskip, \lineskip and \lineskiplimit in TeX, I also know \baselineskip, \baselinestretch, \linespread and the second argument of \fontsize in LaTeX. However, I get confused when I meet the phrase 'double spacing' and setspace package.

The question is, which dimension is doubled? Is it \baselineskip, or the skip between bottom and top of the two lines (something like \lineskip), or some dimension else?

I read the article about leading in Wikipedia. It seems that the original meaning of leading is \lineskip. In Bringhurst's book (The Elements Of Typographic Style), \baselineskip is called a basic leading, total leading, while \lineskip is the added leading, but they are never doubled.

In LaTeX, the basic total leading is the second argument of \fontsize, which is set to \baselineskip. For example, normal font size is 10pt with 12pt of \baselineskip. So, does double spacing mean \linespread{2}? Or it implies a 10pt + 2x(12pt-2pt) = 14pt of TeX's \baselineskip, say, \linespread{1.16667}?

Microsoft Word tells me it should be the former. 'Double' line spacing means \linespread{2} in LaTeX.

(In word, font size 10pt, single spacing gets 12pt baseline skip; double spacing gets 24pt)

setspace.sty tells me both are wrong. \doublespacing is defined as \setstretch{1.667}. (The value is slightly changed to fit different \baselinespace) That is to say, 'double spacing' means the baseline skip is double length of font size. (1.667x12pt = 20pt = 2x10pt.) Why?

(Using setspace, font size 10pt, \singlespacing gets 12pt baseline skip; \doublespacing gets 20pt)

The more I read, the more confused I get. Can anyone help me to clarify the concept?

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I think there is no precise definition. I think in practice 'double-spaced' basically means 'enough space between the lines for you to pencil in comments and corrections'. – Lev Bishop Mar 17 '11 at 17:30
Thanks for all the answers and comments. I accepted meep.meep's answer — the first one. Now I believe that double spacing means doubled \baselineskip. setspace defined a strange, but maybe widely used version. I would suggest my friends to use setspace package with \setstretch{2} or \begin{spacing}{2} for 'precise' double spacing if required. – Leo Liu Mar 19 '11 at 5:27
Ignore the naysayers. I found this to be quite interesting. I didn't realize that setspace got it "wrong." – TH. Mar 19 '11 at 10:01

I had this discussion once with a friend who had a printers education (Sorry, don't know the right english term). I don't remember the details, but basically she said that the setspace package doesn't calculate the line spacing correctly by it's universally defined formula. According to her, \linespread{2} sets the spaces correctly. However, I myself prefer setspace while working with a 1.5 line space, because I think it looks better. Maybe that was also the authors' intention.

(I would be happy if a more sophisticated answer comes along .)

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 Thank you. And maybe a typo: \linespread{2} or \setstretch{2}. – Leo Liu Mar 18 '11 at 11:47 @Leo Liu: You're right. As you normally shouldn't maipulate baselinestretch I changed it to linespread. – meep.meep Mar 18 '11 at 12:08

I'm pretty sure the origin of 'double spacing' is from the time of mechanical typewriters. I've learned touch typing on my mother's machine: You had a "carriage return" lever that returned the carriage (so that you could start at the beginning of the line again) and that at the same time moved the paper (in two distinct steps) forward to the next line. Since one of those "steps" is half a line, you could produce both 1.5 line spacing and double line spacing. In this sense 'double spacing' means doubling the distance between the baselines.

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Thank you for your information. – Leo Liu Mar 19 '11 at 5:06
The typewriters I've know (and loved) have a gearwheel on the roller with the gears at one-half line intervals (ie. 0.5\baselineskip). There's a cam, set by a lever, which positions a detent in such a way as to make the return advance the roller by two, three, or four notches, giving you single-, one-and-a-half-, or double-spacing (in typewriter-speak, of course). – Brent.Longborough Sep 30 '11 at 16:25

I do find the discussion rather pointless. The old doublespace package decided that "doublespacing" means twice the \baselineskip. setspacedecided that "% one and a half spacing is 1.5 x pt size" and "% double spacing is 2 x pt size". Perhaps the author of setspacethought that as double spacing is already bad enough this would minimize the damage. Whatever is the reason of the settings in setspace: If you want other values, it is easy enough to adjust them.

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I agree that this is a kind of pointless discussion. One of the main reasons for setspace's existence is the fact that most, if not all US universities require theses and dissertations to be "double spaced". They don't define it, and they know absolutely nothing about typesetting, but they do check that your thesis meets their crazy requirements. setspace's doublespacing option meets those requirements. So it's operationally defined. – Alan Munn Mar 18 '11 at 17:26
Thank you. That't why I think the concept is confusable. I know how to ajust line spacing. Since then I decided to specify the parameters myself for my own documents. However, I must decide to use \linespread{2}\selectfont or \setstretch{2} or \doublespacing, if I am asked to typeset a double spaced thesis, and the ones ask me know nothing about TeX (and typography) at all. – Leo Liu Mar 19 '11 at 4:53
@Alan: I agree that it's boring. Many of the requirements come from the parameters of MS Word, Ooo Writer, etc. It seems that setspace defined a different version of double spacing, but those who ask for double spacing documents may be satisfied with both \setstretch{2} and \doublespacing, although they're different. – Leo Liu Mar 19 '11 at 5:05