I'm seeing quite a few measurement conversion relating gems, but I haven't been able to find one that will select the best/closest unit.
For example
If I give the gem the measurement of
9 inches + 6 inches
I'm trying to get the result
1 foot, 3 inches
The conversion tools I've seen, I'd have to tell the convertor to try to convert to feet, and then decide which is the most appropriate measurement.
Not sure how complicated you wanted to get but for your example I did this:
With the output of:
Certainly I restricted it to feet/inches but you can abstract it out if necessary (inches & yards, feet & yards, etc.)