There are some pitfalls when it comes to data usage. LTE (4G) data charges can add up quickly, especially when tethering. I write this from the perspective of a MacBook, iPhone, and iPad user, who uses those devices heavily and interchangeably.

Habits Which Need a Lot of Data

  • Updating iOS apps. I have about 140 apps for iPhone and iPad. The average app size increases every year. Mayor apps like Facebook, LinkedIn, Skype etc. are most likely bigger and weigh 100–150 MB each. Those get updated every other week. While not the full app will be downloaded for the update, in my case it still adds up to 5–10 GB each month.
  • Watching YouTube a lot or downloading movies and TV shows. Well, no surprise. Video uses a lot of data. The higher the video resolution and the longer the video, the higher the data. A high-quality FullHD video will have about 2–2.5 GB per hour.
  • Video chat. It’s video, see above, but the resolutions are mostly lower than the movie ones.
  • Streaming music. A high-quality music stream (256 Kbit/s) uses about 2 MB per minute and 112.5 MB per hour. So nine hours of music streaming while working and commuting uses about 1 GB of data a day.
  • Audio books. Audio books are like music. A high-quality audio book (128 Kbit/s) uses half of what high-quality music does per minute.
  • Online and iCloud backup. iOS devices get automatically backed-up daily if connected to power, locked and being on Wi-Fi. The next backup size can be seen at Settings > (The Top-most Entry Showing Your Name) > iCloud > Manage Storage > Backups > (The Current Device) > Next Backup Size. But these numbers change hourly depending on what has changed on the device.
  • iCloud Photo Library. If enabled this will upload all photos and videos shot by this device to iCloud so they can be synced to different devices and are effectively backed-up. Depending on the amount of photos and videos shot on a day, these can add up to hundreds of megabytes or even gigabytes. Uploads are only done on mobile, if this is enabled in Settings > Photos > Mobile Data > Mobile Data. Apple might change the default in the future, so better check the current setting.

Habits Which Use a Medium Amount of Data

  • Text messaging whith sharing images and videos in this chat. Images use a couple of megabytes each. Videos use much more, likely dozens to hundreds of megabytes.
  • Email having attachments. Attachments can be large, up to the tens of megabytes. Images in emails are in most cases either attachments or have to be downloaded from the internet while viewing.
  • Web pages. Web pages are mostly small, because it’s just text. But most web pages have many images, fonts, styling, scripts (which add useful behavior), and tracking and ad scripts. Fancier web pages start at 1 MB per page and can go up to 10+ MB. Homepages use more data than article pages, because they have many teasers to articles. Scrolling down a long homepage may load data in the background, which can multiply the amount of data used for this page if scrolled long enough.
  • Maps. Maps use a medium amount of data. If you use maps for navigation and drive and hundreds of kilometers or miles, data usage can add up to hundreds of megabytes. Traditional navigation apps have offline map data so they don’t have to download any data to display the route.
  • Subscribing to Feeds. If you use a podcasting app or a RSS reader, both with many feeds, then it depends on the update interval. Each interval the feed for each subscribed podcast or website will be downloaded, regardless if anything has changed. If the feeds are large and have many entries like for podcast, you can have single to double digit megabyte downloads each day. If you update those feeds every hour or even faster, then it can amount to a couple hundred of megabytes.

Habits Which Don’t Need a Lot of Data

  • Text messaging. Text uses a negligible amount of data compared to other formats. If you attach images and videos the amount of data increases massively.
  • Email without attachments. Emails without attachments and images are mostly text. See Text messaging.
  • Notifications. Notifications are very small amounts of text.
  • Location data. Location data uses a very small amount. See above if you use maps.
  • Background updates. In general they don’t use a lot of data if the app is conscious about data usage.

Things Eating Your Data Allowance You Don’t Know of

  • Automatic app updates. Automatic app updates run in the background on iOS and, if enabled, on macOS. They only run on Wi-Fi, but Macs can be tethered and won’t know about the phone using mobile data (they know if you tether to an iPhone or iPad but only silently stop syncing the photos app). Updates on iOS are much more frequent. It’s also likely that most people have more iOS apps than macOS apps, because they are cheaper and big companies have to have mobile apps to be present on smartphones, but get away with having just a website on desktop, like Facebook. An average non-gaming iOS app may be 50 MB in size, gaming apps are in the hundreds of megabytes. Some apps like Facebook, Facebook Messenger or TripAdvisor for example are updated every two weeks. And they are 80–200 MB in size. At least iOS only downloads changes and not the whole app again.
  • Podcast subscriptions. If you enabled automatic downloads of new podcast episodes on mobile and didn’t restrict it to only download on Wi-Fi, you may download a lot of data. This depends on the amount of subscriptions and updates to those. Podcasts use a quarter to half of what music uses in general. But they are much longer than the average song so they can be easily 100 MB in size each.

Bottom Line

The bottom line is simple: Video, music streaming and app updates use the most data. The rest depends on your usage pattern and frequency. This is no surprise, but sometimes it’s hard to understand for what the data has been used for. And hopefully in the near future mobile data plans will have much more data included for a reasonable price. Then only video and excessive music streaming will be an issue.