My iPhone 5 is using tons of data...

No, not seeing it due to I rarely view video on cellular.

Numbers might be a bit off, but seem to recall 720p video is about 800-900MB for 1 hr of video. Double for 1080p videos.

So, depending on the format of the video and length (and add in ads that get thrown at someone), yeah, can eat up data quickly.

And throw in Facebook, mail, audio streaming, automatic updating, iTunes Match, automatic downloading of purchased items, push notification, maps, iCloud contacts/reminders/calendar, photo streams/backup, etc etc.

Settings > Cellular and scroll to bottom to see what apps are eating up the data plan.

 

As NoBoMac said, check the cellular settings, but go to the bottom and reset the statistics. Then go back in a few days now and look at all the apps listed and see what they've been up to.

You might be able to get an answer now by looking at them, but since the list contains the data usage for all time it'll probably be hard to see what's going on.

Do the reset, wait 2 days, and then check again.

 

My iphone 6+ used 1.2gb of data last night while on wifi.. something is not right. Currently trying to figure out what is wrong.

 

That's very strange, and I would definitely check your usage as suggested above. I also have an iPhone 5 on Verizon and only saw that kind of usage when I didn't use wifi much. My billing cycle turned over on November 7th, and I've used 2% of our 6gb plan. In total my family has used 5%.

It does seem very strange if your habits haven't changed. I know when I switched to my iPhone 5 from a BlackBerry, my data usage skyrocketed to 4 or 5gb from less than 1gb. I'm not sure if it was my phone, the slight change in usage, or Verizon trying to get my dad to buy a bigger data plan. He kept it the same, and once I started using wifi more it went down to a reasonable amount.

 

Sorry to bump an old thread, but my daughters 6 just started using an insane amount of data, pushing us to the top of our cap. Typically we use ~4 gb between 4 iPhones on the 10 gb plan. Her phone suddenly used 7.5 gb this month, with huge transfers of 1 gb at set times. According to my account, at 3 pm it dumped 1 g of data, and then again at 9 pm. It was connected to our home wifi the entire time. Something strange is going on here. Turned cellular data off for a bunch of things, I'll see how it goes.

 

It seems to be an iOS 8 bug where it shows it is connected to wifi, but actually uses the cellular data. I guess the only solution now is to turn off cellular data when you don't want to use it, and turn it on when you do want to use it.

 

Facebook is a big killer, turn off automatic loading of videos

 

To add to what eclipse01 said:

Go through General > Background App Refresh and turn off almost everything (lots of stuff want refresh but really doesn't need it, imo).

And anything associated with iTunes store re: automatic downloads (tick off "Use Cellular"). Suspect this might be it: phone phoning home and getting app updates, music purchases.

Podcasts: disable background refresh.

Disable photo stream.

 

agreed. i went over my data last month and the culprit was Facebook. Stupid auto-loading videos.

I just disabled it

also, I'm on an iPhone 6.

 

Did this last night, only used 8 mb last night and today. Seems to have solved the problem.