[thelist] CSS ? size of text input

[Michael Collins]

I want to specify the width of a text input on a form using the CSS 
width property. I am used to specifying with a character length such 
as:

<input type="text" name="field" value="" size="30">

How do I calculate from a size specified by the HTML size attribute 
to the CSS width so it will appear the same size as in:

<input type="text" name="field" value="" size="30" style="width:?;">