Datasheet - Electrical Characteristics Section. For the 16F819 it's Section 15.

Don't look at my next paragraph... go read the Datasheet first...

OK, now you've read it, you've wasted your time (but admit it was fun!), because the current drain will depend on your I/O's (ie what's sourcing and what's sinking), what internal hardware you've enabled (ADC's weak pull-up's internal voltage references etc etc). You get the drift. You just can't calculate it that easy.

You build your circuit, stick your DMM on Amps and measure... If you want to really feel good, you measure on the 10A range and it'll show zero... Note that when measuring on very low (single figure) uA ranges, your meter will impact quite a high series resistance which can throw the operation of your circuit as well as give you a false reading.