CSS fonts rem trick: 62.5% or 6.25%

Question

I would like to use font sizing with REM and on internet I found following trick:

html { font-size: 62.5%; } 
body { font-size: 1.4rem; } /* =14px */
h1   { font-size: 2.4rem; } /* =24px */

due to set font-size: 62.5%; coversion rem <-> px (pixels) is very easy (just divide pixel value by 10).

However I wonder - why not use value 6.25% - in that case our trick will be look like this:

html { font-size: 6.25%; } 
body { font-size: 14rem; } /* =14px */
h1   { font-size: 24rem; } /* =24px */

and this approach look to be more direct that for value 62.5% (we can convert rem to px without changing number value) - however I have question - why people "on internet" not use this approach - may be it cause some problems (that I'm not aware)?

Answer 1

You could use 6.25% so that you get your nice 1:1 rem values, then set font-size: 16em; on body to get the best of both worlds. It'll fix the tiny font problem in old browsers, and browsers that do understand your rem declarations will ignore it by looking to html's font-size when calculating sizes. As far as I can tell there are no drawbacks to doing it this way and you actually get a better sized fallback than you do with 62.5%, but there may be something I've missed so use it with caution.