For cell, hardly anything, I have a 750MB cap which is kinda low so I only use it in oddball situations. In general I don't do much data transfers on my cell. Sitting at 2MB for the month lol. That's probably from misc traffic that happens in the background while I'm out of wifi range.
At home, no idea, since they got rid of the RRD graphs in pfsense. I'm still pissed at that. I never looked into another way to monitor my usage. I have pushed TBs in days at times, but in average I probably use no more than like 200-300GB/mo. Thankfully I have no cap for my home internet so I don't really have to worry about how much I use.