I posted the following on the Google+ group comp.soft-sys.math.mathematica and had no luck with responses. I've done a Google search and, to the best of my ability, used the documentation center.

The post I made was as follows:

I continue to receive "Unable to interpret unit specification m/s" (for example, but almost anything I attempt returns this message) with input: UnitConvert[55 mi/h,"m/s"] or UnitConvert[55 mi/h,m/s] or any other combination of quotes, omitted quotes, etc. Even the prediction/suggestion box, when I execute Quantity[55,"mi/hour"}, after it returns 55 mi/h, if I type in any combination of m/s, "m"/"s", "m/s", etc. into the box that opens when I select "Convert" in the prediction box yields the same "unable to interpret unit specification.

What am I missing? (As you may gather, I'm a Mathematica novice.)

  • 2
    $\begingroup$ Try UnitConvert[Quantity[55 , "Miles"/"Hours"], "Meters"/"Seconds"]. $\endgroup$ Commented Dec 18, 2012 at 21:09
  • $\begingroup$ That's the sam as the answer I posted to MathGroup this morning. (Which raises a protocol/meta-question: should folks be posting the same question to both MathGroup and here?) $\endgroup$
    – murray
    Commented Dec 18, 2012 at 21:24
  • $\begingroup$ @murray ask it on Mathematica Meta. I believe it was discussed, but I cannot remember where. $\endgroup$
    – rcollyer
    Commented Dec 18, 2012 at 21:47
  • $\begingroup$ @murray meta.mathematica.stackexchange.com/q/367/16 $\endgroup$
    – acl
    Commented Dec 18, 2012 at 22:24

1 Answer 1


It seems, if you are not going to use the "proper long name", you need to use Quantity Try

UnitConvert[Quantity[55, "mi/hour"], Quantity["m/s"]]
  • $\begingroup$ +1, exactly. You must use Quantity, otherwise it may not recognize what you are doing. $\endgroup$
    – rcollyer
    Commented Dec 18, 2012 at 21:20
  • $\begingroup$ Thanks.Those work but the UnitConvert page in the Documentation Center and the sure doesn't make it seem like all that is necessary. For example: UnitConvert[Quantity[8.2,"Miles"],"Pounds"]]. $\endgroup$
    – user5091
    Commented Dec 18, 2012 at 22:16
  • $\begingroup$ @user5091, There's a "full" name for each unit, and then there are ways that you can type it that get properly recognized because WolframAlpha understands what you mean. If you do InputForm[Quantity["m"]] you'll see what I mean. That translantion only seems to be done inside Quantity. If you use the "full" name, you don't need the Quantity in UnitConvert $\endgroup$
    – Rojo
    Commented Dec 19, 2012 at 0:48
  • $\begingroup$ I agree however that it shouldn't be necessary to type Quantity. Perhaps it will be changed in the next upgrade. $\endgroup$
    – Rojo
    Commented Dec 19, 2012 at 0:50

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