Units for mass in the available energy formula

[HarryDaniels]

In the formula of available energy of a stationary particle and a moving particle:

Ea=(square route of)2MtC^2+(MtC^2)^2+(MkC^2)^2

where:
Mt= mass of stationary particle
Mk= kinetic energy of stationary particle
C= speed of light (299,792,458)

Can someone tell me what the unit of measurement for the mass of the particle.
Thanks

 

[mgb_phys]

Assuming that C is in m/s and E is in Joules = it would be Kg

 

[HarryDaniels]

This may sound like a stupid question, but why?

 

[mgb_phys]

Pretty much from the definition of the Joule

In CGS you would need mass in g, speed in cm/s and you would get an answer in Ergs.
But in imperial units you would need a conversion factor for lbs, ft/s and BTU/HP - it's just that for metric systems the definition of the unit of energy makes the factor =1