I looked into a number of different approaches for calculating cellular data use. Each of the big American carriers offers an app or web tool for monitoring data consumption. But I recommend against those solutions because in my testing, they were generally time-consuming or poorly designed.
Instead, the quickest way to monitor your data use is by simply using your phone. Each carrier has a hidden code that you can punch into your phone to get an update on data use.
For AT&T subscribers, the method is simple. You place a phone call to *DATA# (*3282#). AT&T will send a text message showing the amount of megabytes you have used out of your monthly allotment. It showed that so far this month I have used 464 megabytes out of 3 gigabytes.
[...] Similarly, Sprint customers can send a text message containing the word "Usage" to the number 1311 and get a text message with a data report. T-Mobile subscribers can place a call to #WEB# (#932#) to receive a quick data summary.
(Score: 1, Interesting) by Anonymous Coward on Monday December 28 2015, @09:55PM
This does not work as well if you commonly mooch from WiFi hotspots.
My own cellular hot-spot forgets the data usage every time I power it down :P
(Score: 2) by Nerdfest on Tuesday December 29 2015, @01:22AM
The data counters in Android handle this perfectly. I tend to be on hotspots most of the day and mobile just when out or in transit from work. It's always been exceptionally accurate from what I can tell.
(Score: 0) by Anonymous Coward on Tuesday December 29 2015, @03:12AM
I meant that I never turn on the cellular radio.
So I have a situation where some of the bits are metered, while others are not (or metered as a much lower rate). These are all blended together in the same chart.