For example, I want to convert 179 centimeters into 5 feet and 10.4724 inches instead of 70.4724 inches (as this website did). Maybe in the future I would need to convert days to {years, months, days} combination, degrees to {degrees, minutes, seconds}, etc. I can indeed write some codes to perform the task, but after all personal codes are full of flaws and lack of exception handling, so I am looking for a built-in function.

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    – bbgodfrey
    Commented Jan 20, 2015 at 23:57
  • 1
    $\begingroup$ In WolframAlpha (or Mathematica after "==") just type "179 centimeters in English units". There are built-in functions for time in Mathematica, however, such as FromDate[], all well documented. $\endgroup$ Commented Jan 21, 2015 at 0:06
  • $\begingroup$ @DavidG.Stork Yes, $DateList[{y,m,d,h,m,s}]$ can solve some of the problems concerning time, but it has many restrictions: {y,m,d} cannot be 0; cannot display 3.14 days, but 3 days 3 hours 21 minutes 36 seconds instead. $\endgroup$ Commented Jan 21, 2015 at 0:27
  • $\begingroup$ Could you please give one very specific example of the kind of problem you want solved? The conversion of days to {years, months, days} is straightforward. What else? $\endgroup$ Commented Jan 21, 2015 at 0:29
  • $\begingroup$ @DavidG.Stork it is interesting that these are called English units. I wondered what W|A would tell me for "32 hogsheads + 9 pints + 17 gills in French units". It replied that this is $2.062\times10^{11}$ cubic Frenches. You learn something new every day. Oh, and it also thinks that this is a measure of engine displacement, although the French gauge system is used to describe the diameter of catheters. $\endgroup$ Commented Jan 21, 2015 at 0:33

3 Answers 3

UnitConvert[Quantity[179., "Centimeters"], MixedRadix["Feet", "Inches"]]


Quantity[MixedRadix[5, 10.472440944881885`], MixedRadix["Feet", "Inches"]]

which formats as 5'10.4724"

  • $\begingroup$ +1 It is a very nice undocumented feature! $\endgroup$
    – ybeltukov
    Commented Jan 21, 2015 at 2:34
  • $\begingroup$ @ybeltukov I actually didn't know this was undocumented; searching in the documentation center gets no results (!!!) but I'm sure I read this in the documentation center somewhere. $\endgroup$ Commented Jan 21, 2015 at 2:37
  • $\begingroup$ Is there an undocumented Tag? This is not the first example. Reasonable to expect WRI at some point may mine this site. $\endgroup$ Commented Jan 21, 2015 at 4:21
  • $\begingroup$ @alancalvitti undocumented tag added. $\endgroup$ Commented Jan 21, 2015 at 4:22
  • 1
    $\begingroup$ @george2079 UnitConvert[Quantity["Meter"], MixedRadix["Feet", "Inches", "Inches"]] becomes 3'3"47/127". Not power-of-two fractions though. $\endgroup$ Commented Jan 23, 2015 at 23:40

There is no such build-in function. However, one can write it easily

convert[q_Quantity, units_List] := MapAt[{Total@#} &, #, -1][[2 ;;, 1]] &@
  FoldList[Through@{IntegerPart, FractionalPart}[Last@#/#2] #2 &,
   {q, q}, Reverse@Sort[Quantity /@ units]]

convert[Quantity[179., "Centimeters"], {"Feets", "Inches"}]
(* {Quantity[5, "Feet"], Quantity[10.4724, "Inches"]} *)

convert[Quantity[1.2345, "Meter"], {"Millimeters", "Centimeters"}]
(*{Quantity[123, "Centimeters"], Quantity[4.5, "Millimeters"]}*)

convert[Quantity[1.2345, "Degree"], {"Degree", "ArcMinute", "ArcSecond"}]
(*{Quantity[1, "AngularDegrees"], Quantity[14, "ArcMinutes"], Quantity[4.2, "ArcSeconds"]}*)

10.4 introduces MixedMagnitude and MixedUnit, eg:

Quantity[MixedMagnitude[{1/2, 2, 3}], 
 MixedUnit[{"Hours", "Minutes", "Seconds"}]]

which btw, renders with bogus DisplayForm

0 h 32 min 3 s

And try all 0's.


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