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, @11:08PM
The examples in the summary make me glad I switched to Ting mobile [ting.com] a while back. They have a great dashboard [ting.com] you can check whenever you want.
I have an account, but I don't want to be accused of gold-digging (there's a referral bonus) so I'm posting anonymously. I'm just happy that there's a company who doesn't jerk you around as much as the others.