New
#1
The unit is a bit of a joke and does not really mean the hand unit which we use in Britain to measure horses. If you put in longer lengths it will refer to jumbo jets instead of hands. Shorter distances refer to paper clips. My guess is the Microsoft hand is the distance between the end of the little finger and thumb, about 18cm.
I think you've got it :) Its confusing because the 'hand' is a (sort of) recognised 'unit'. If you enter 'convert hand to cm' or vice versa into a search engine then are lots of offerings, all giving the 'correct' answer.
I've gone on and logged this as an 'issue' with the calculator using the Windows feedback tool. I'm pretty sure Phil has the answer, although when you ask Bing or Google to convert 'cm to hands' you get consistent and valid results. Maybe this one has backfired on MS.
Actually the 'old' calculator (which imported courtesy Winaero) also offers hands along with rods, chains, spans, yards (but not alas furlongs, perches or chains....)