@LovesTha @cpontvieux @mhoye @xek "k" for "kilo" as in "thousands" is lower-case.
The "official" notation, as mentioned by Cyrille, is:
km/h or km h⁻¹
If you (or anyone passing) happens to be interested / are not already aware... the organisation who determines such "official" things is the BIPM. A description/documentation of the SI system of units (overseen by the BIPM) can be found on their website.
km/h is not an SI unit... just "accepted" for use with the SI.
@level98 @cpontvieux @mhoye @xek Yes, techically KMPH is Kelvin Mega Pascals Hecto