Can someone tell me the difference between using the units of pressure "bar" and "barg"?

a bar is 10^5 Pa absolute pressure a barg is 10^5 Pa gauge pressure.

 

say a pressure gauge reads 20 barg this means the pressure is 20 bar above atmospheric pressure or 21 bar absolute pressure assuming atmospheric pressure that day is 1 bar. the barg is useful for working out specifications for equipment and machinery.

 

edit: spelt gauge as guage D'OH!

Now i understand it better!! Quite simple but when you don’t know it, it’s not so simple!!! Thank you so much!!

no bother. try http://www.unc.edu/~rowlett/units/index.html if you need to know what any other units mean