[DerekAsirvadem]

There are no "preferences" for that exact requirement.

However, most of us find the RulerUnits and RulerScale (View/Rulers to see them, just below the Toolbar) adequate for that purpose.

Of course, using Metric rather than Imperial units eliminates a swag of problems, but you are probably quite used to the swag. Many decades ago, when I was using Imperial units, it helped a lot to know what 1/16" was in decimal, so that converted values were instantly recognisable as a valid 1/16th or not.

Correctly setting your Grid (for whatever your purpose is), that is Major and MinorGridSpacing via the Inspector/Canvas/Grid is also important.

If you want to "always show {fractions|decimals}" in the various Inspector boxes, post a Feature Request.