# How to calculate a new length?

What I want to do is calculate the actual size between the edge of the paper, and my header. `\evenmarginsize` and `\oddmarginsize` do not do this.

``````\settowidth{\msize}{((\paperwidth - \textwidth)/2)}
``````

Doesn't seem to work, how can this be done?

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1. You don't say which edge of the paper. On first reading, because you are talking about the header, I thought the top edge. 2. The commands `\evenmarginsize` and `\oddmarginsize` don't exist. Perhaps you meant `\oddsidemargin` and `\evensidemargin`. 3. `\settowidth` takes a piece of text and calculates its width. For what you want, use `\setlength` and you need the `calc` package to use algebraic notation. 4. One more thing: supply a compilable file that shows what you tried. –  Dan Dec 9 '13 at 3:13
1) The left hand side, when I first tried this I didn't think it mattered. 2) Yes, those are the correct commands. My memory mixed them up. 3) Below is a solution without calc. 4) Didn't need to. Oh, and one more thing, calm the attitude Mr. Keyboard Warrior. –  NictraSavios Dec 9 '13 at 8:41

Use the e-TeX structure:

``````\newlength{\msize}
\setlength{\msize}{\dimexpr(\paperwidth-\textwidth)/2\relax}
``````

The macro `\settowidth` is used with finding the width of a portion of text such as in:

`````` \newlength{\mytextwidth}
\settowidth{\mytextwidth}{This is some text whose width I'm measuring}
``````

The documentation can be found by running `texdoc etex` from the command line. Amoung other things, e-TeX provides several nice commands to facilitate calculations using `\dimexpr`, `\numexpr`, and several other flavors. Since I've discovered these, I find I don't use the `calc` package that much anymore.

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Documentation Please :)! –  NictraSavios Dec 8 '13 at 19:54
``````\usepackage{calc}

...

\setlength{\msize}{0.5\paperwidth-0.5\textwidth}
``````

However, I recommend you looking at the `hcentering` option of the package `geometry`.

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Not trying to centre the header. –  NictraSavios Dec 8 '13 at 19:55
Well, you obviously do some calculation of the page geometry. I only suggest that you might have a look at the package above, because you might save yourself a lot of time not doing something that has been done before ;) –  tohecz Dec 8 '13 at 19:56
Haha I checked it out, it wasn't what I wanted. Thank you though –  NictraSavios Dec 9 '13 at 8:43