# canonical units for defining white space in a beamer presentation?

When using \hspace and \vspace, I often run into a decision of which units to use. In many examples I see the use of ex, cm, mm, pt, in, and so on. I also use .1\textwidth or .1\textheight. I wonder if there is a standard unit that makes sense for moving boxes or figures in beamer; I am recently consolidating all of my vertical space units to ex but is this sensible? Is there an equivalent horizontal space unit which corresponds to character width (for a monospace font), for instance?

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You can use em for horizontal space. See this for more info: tex.stackexchange.com/questions/8260/… ,especially Herbert's last answer and this one tex.stackexchange.com/questions/4239/… –  percusse Sep 30 '12 at 12:32
Some units change depending on the type size. For example, if your \documentclass has a 10pt (11pt) option then 1em will be equal to 10pt (11pt). Some lengths are better expressed relative to the type size, in which case you should use em or ex. Other units are better expressed in absolute units such as cm, m, and even inch. –  Marc van Dongen Sep 30 '12 at 12:43