Streaming Quality Calculator

Why "my broadband is fast enough" is the wrong question

Most people frame it as a single number: my line is 80 Mbps, so it must be fine. The trouble is that streaming quality is a per-stream cost, and a household is rarely doing one thing at a time. A film in the lounge, an iPad in the kitchen, a Switch downloading an update, someone on a video call upstairs. Each of those takes its own slice of the line. The right question is not "is my broadband fast enough", it is "is my broadband fast enough for everything I am asking it to do at once". That is what this calculator works out.

The bitrate ladders, explained

Each streaming service publishes a recommended download speed for each quality tier. They are not identical. Netflix's published figure for 4K HDR is around 25 Mbps, with Dolby Vision titles climbing higher again. Disney+ sits in roughly the same ballpark for 4K. Prime Video tends to come in a touch lower in practice. YouTube is the outlier: because it uses VP9 and now AV1, both more efficient codecs than HEVC, the same picture quality fits in noticeably less bandwidth. A YouTube 4K stream can run at 15 to 20 Mbps where Netflix 4K wants 25.

SD and HD are simpler. Across all the major services, 480p sits around 3 Mbps, 720p around 5 Mbps, and 1080p around 8 Mbps. Two 1080p streams on Netflix or Disney+ is roughly 16 Mbps of demand, plus your headroom, plus whatever else is running. On a 50 Mbps line, that is fine. On a 30 Mbps line with someone on a Teams call, you are going to feel it.

What headroom is for

The headroom slider exists because nobody actually uses 100% of their line for one thing. There is always a smart speaker checking in, a laptop syncing iCloud, a phone uploading photos in the background. The default 20% is the realistic middle. If it is a quiet evening and the rest of the house has gone to bed, drop it to 10%. If someone is on a Zoom call or backing up to Backblaze, push it to 30 or 40%. The verdict at the bottom of the page bands accordingly: Comfortable means at least a quarter spare, Tight means it just about fits, Insufficient means the maths does not work and your stream will downgrade or buffer.

Concurrent streams are the killer

Single-stream maths is reassuring. Concurrent maths is honest. Three people each watching their own 1080p Netflix is 24 Mbps of demand at minimum, and that is before the family Hue lights and the smart doorbell get a look-in. On a 35 Mbps line, that is already past the comfort threshold. On a 25 Mbps line, somebody is dropping to 720p whether they like it or not. The "highest tier this line can hold at your concurrency" output is the practical answer: given how many streams you have asked for, what is the best picture quality the line can actually hold steady?

Common mistakes when planning

• Using the headline ad speed. Most lines, especially over Wi-Fi, sit a fair bit under the ad number once you are a few rooms away from the router. Run a real speed test on the device that will be doing the streaming.
• Forgetting upload-bound activity. Cloud backup and video calls are upload-bound, and the household share that calculator does not show. If anyone in the house works from home, plan around their upload as well.
• Treating 4K HDR and 4K Dolby Vision as the same thing. Netflix's Dolby Vision titles run noticeably hungrier than its standard 4K HDR. If a film is showing the DV badge, expect closer to 40 Mbps than 25.
• Assuming Wi-Fi is the same as the line. A 900 Mbps full fibre line still feels rotten over a ten-year-old router two walls away. The bottleneck is sometimes inside the house.

What to do if the verdict says Insufficient

Three options, in order of cost. First, drop the target quality. 1080p is genuinely fine for most rooms, especially under 50 inches; the gap to 4K is smaller in practice than the gap from 720p to 1080p. Second, sort the Wi-Fi: a mesh system or a wired drop to the main TV often unlocks a chunk of the speed you are already paying for. Third, upgrade the line. Full fibre is the answer if it is available, and across most of the UK it is increasingly available. If you are still on FTTC and 4K matters to you, an upgrade is the genuine fix.

Related calculators

Streaming bitrate is one demand on the line. These cover the rest of the household.

• Work out how much speed your household needs
• Check the speed you're actually getting
• Check how latency affects calls and gaming
• Estimate the time on a one-off download