\begin{definition}[Definition:Kilogram]
The '''kilogram''' is the SI base unit of mass.
It is defined as being equal to:
:The fixed numerical value of the Planck constant $h$ to be $6 \cdotp 62607015 \times 10^{-34}$ when expressed in the unit Joule seconds.
The Joule second is equal to $1 \, \mathrm {kg} \, \mathrm m^2 \, \mathrm s^{−1}$, where the metre and the second are defined in terms of:
:the speed of light $c$
:the time of transition between the two hyperfine levels of the ground state of the caesium $133$ atom at rest at $0 \, \mathrm K$.
{{explain|The above does not make immediate sense. It needs to be better explained. The kilogram is not "equal to" Planck's constant, which the above seems to imply.}}
{{begin-eqn}}
{{eqn | o = 
      | r = 1
      | c = '''kilogram'''
}}
{{eqn | r = 1000
      | c = grams
}}
{{end-eqn}}
\end{definition}