How much mobile data you need per month depends almost entirely on one thing: how many hours of video you watch on mobile data, and at what quality. Everything else, messaging, maps, music, browsing, adds up to a fraction of that. A person who never watches video away from Wi-Fi can live on a small plan; a person who watches an hour of HD video on the train every day needs a plan measured in tens of gigabytes.
The fastest way to get your own number is our data usage calculator: set the hours per day for each activity and it produces a monthly figure. Below is what sits behind that figure, where the surprises come from, and what a VPN does to it.
The one variable that matters: video quality
The calculator's video row assumes roughly 0.7 GB per hour at standard definition, about 3 GB per hour at HD, and about 7 GB per hour at 4K. Those are the figures that swing a monthly total from a few gigabytes to a hundred. The same one-hour show costs four times as much in HD as in SD, and ten times as much in 4K, and on a phone screen the difference between SD and HD is far smaller than the difference in your bill.
If you take one thing from this article: the video quality setting in your apps, not the number of apps you use, is what decides your plan.
What the rest costs, roughly
Music uses a small fraction of what video does; an hour of listening is closer to a few minutes of HD video than to an hour of it. Video calls sit between the two, and the camera on both sides matters far more than the length of the call; audio-only calls are cheap. Social feeds and browsing are unpredictable for one reason: autoplaying video. A feed with autoplay on behaves like low-quality video; the same feed with autoplay off behaves like text and photos. Maps are small once the area is downloaded offline. Gaming itself is small; game downloads and updates are large, and they are the usual culprit when a plan disappears overnight.
Estimate your month in three steps
- For each activity, be honest about hours per day on mobile data, not total hours. Most video happens on home Wi-Fi and does not count.
- Multiply by the per-hour figure for that activity and by the days in a month. The calculator does this for you and lets you change the video quality separately.
- Add a margin of roughly a third. Background activity and the surprises below are what the margin is for, and a plan that is slightly too big costs less than the overage on one that is slightly too small.
Where the surprises come from
Photo and video backup on mobile data. A phone that uploads every photo to the cloud as soon as it is taken can use more in a day at the beach than in a week of messaging. Set backup to Wi-Fi only.
Autoplay. Feeds, shopping apps and news sites play video without asking. Turn autoplay off on mobile data in each app that has the setting.
App and system updates. One system update over mobile data can be larger than a month of browsing. Keep updates on Wi-Fi.
Hotspot. A laptop connected through the phone behaves like a laptop, not like a phone: cloud sync, updates and video calls at desktop quality. Hotspot days are the days most people blow through a plan.
Background refresh. Dozens of apps quietly checking in add up to a small but permanent overhead, and the only cure is to switch background data off for apps that do not need it.
How a VPN changes the number
A VPN adds a small overhead to every packet, because the encryption wraps your traffic in another layer. For ordinary use the addition is a few percent, not a doubling, and video quality settings matter a hundred times more. Where it can matter is in what the tunnel does when it is unstable: reconnections and retries cost data too. The measurement and the ways to keep the overhead small are in Does a VPN use more data.
Travel and roaming
Roaming packages and travel eSIMs are sold by the gigabyte, so the estimate matters more abroad than at home. Two things change on a trip: maps run more, and photos upload more. Two things help: download offline maps and an offline translation pack before you leave, and set every backup and update to Wi-Fi only. Which line to use in a country that filters the internet, and how it interacts with a VPN, is a separate question, covered in eSIM, roaming or a local SIM in China and, more generally, in Do I need a VPN when traveling.
Cutting usage without giving anything up
Drop video to standard definition on mobile data and leave HD for Wi-Fi. Turn autoplay off. Move backups and updates to Wi-Fi. Download music and maps at home. Use the phone's built-in data saver, which does most of this in one switch. None of it changes what you can do; it changes when the bytes are spent.
404 VPN's data usage calculator runs in the browser, with nothing sent to a server, and tells you at the end whether our free plan, 2 GB a day, covers your usage or whether you need more. If you are choosing a mobile plan and a VPN at the same time, start with the calculator, then read about the free plan on the home page.