Streaming is by far the largest share of internet traffic for most households. The amount of data you use depends on three things: the type of content (video or audio), the quality setting, and how many hours you stream across all your devices.
For video, standard definition uses about 0.7 GB per hour, HD about 3 GB, Full HD about 3.5 GB and 4K Ultra HD about 7 GB per hour. Music streaming is much lighter at around 0.15 GB per hour. These are typical averages; each platform compresses video differently and adjusts quality in real time depending on your connection.
To put that in perspective, a household watching two hours of HD per evening uses about 180 GB per month. Add some 4K movies at the weekend and a second person watching on a tablet, and 300–400 GB a month is common. Music, podcasts and social media generally make up a small part of the total.
If you're on a capped plan, the biggest savings come from lowering video quality on small screens, downloading content over Wi-Fi in advance, and turning off autoplay. Most streaming apps offer data-saver settings specifically for mobile networks.
Use the calculator to add every service in your home, set the hours and quality for each, and enter how many devices stream at the same time. You'll see your daily, monthly and yearly usage, a chart of where the data goes, and a recommended plan size.