Purely out of curiosity this morning, since it was 68F outside, I rounded up every air pressure guage I own.  I found 6 pencil style (1 brand new), and 3 dial type (1 brand new).  Not one of them agreed with another (more than 2psi off), or the onboard TPMS.  Even the one that was close to my buddies Acupressure digital guage was off compared to the 2 older dial guages (that were within 2lbs of each other).   

Guess it's time to find a calibrated one.   

You know, it's enough to make your brane hurt...

+1 Jim...
 
I did math all day at work, I choose not to read this...

I have two Accugage dial gauges and one Accutire digital and all read within 1 pound of each other.  Years ago an old mechanic told me to get a good digitial gauge and use it.  I still trust those the most.