How do I automatically size my grid columns so all the text fit?

I tried this but the width is too small:
with this
* replace default column header with custom header class
FOR liColIndex=1 TO .ColumnCount && loop through all grid columns
WITH .Columns(liColIndex)
.width = fsize(.Header1.Caption)
endwith
endfor
endwith

I'm guessing there must be a multiplier?

Thanks