What internet speed for SD, HD, Full HD and 4K streaming?

"Is my connection enough for 4K?" The question comes up constantly, and the usual answer ("you need 25 Mb/s") is both too simple and sometimes wrong. A video stream does not have a single bitrate: it depends on the resolution, the codec used to compress it, the frame rate and the publisher's choices. Your connection, for its part, does not deliver a constant speed: it varies with the time of day, the Wi-Fi and the other uses in the household. This guide gives you reliable orders of magnitude, a calculation method and the right way to measure what you really have.

Megabits, megabytes: do not mix up the units

Internet providers and speed tests express speed in megabits per second (Mb/s or Mbps). Browsers and download managers often show megabytes per second (MB/s). Since a byte is 8 bits, you divide by 8: a 100 Mb/s line downloads at best around 12 MB/s. Many people believe their connection is eight times slower than it is, simply because of this confusion.

This conversion is also used to estimate data consumption, useful if you watch over a mobile connection or a capped plan. A 1 Mb/s stream for one hour amounts to 3,600 megabits, or about 450 MB. From this we get the following rule of thumb: hourly consumption in GB ≈ bitrate in Mb/s × 0.45.

A two-hour film in 4K can therefore use close to 20 GB: enough to quickly exhaust a mobile plan or a hotspot.

Typical bitrates by picture quality

The values below are orders of magnitude observed on streaming services and channels broadcast over the Internet. They are not standards: each publisher sets its own tiers.

Why such wide ranges?

Three factors explain the gap between the bottom and top of each range:

• The codec. For equivalent perceived quality, HEVC (H.265) needs about 30 to 50% less bitrate than H.264, and AV1 does slightly better still. A Full HD channel in H.264 at 8 Mb/s can look like an HEVC stream at 5 Mb/s. Our article on H.264, HEVC and AV1 codecs details these differences.
• The frame rate. Sport at 50 or 60 frames per second demands clearly more bitrate than cinema at 24 frames per second, because there are more frames to encode and more motion.
• The content itself. A news bulletin with a motionless presenter compresses very well; a football match with a scrolling pitch, rain or confetti is much more demanding.

Constant or variable bitrate

Most streams are encoded at variable bitrate: the average may be 8 Mb/s with peaks at 15 Mb/s in busy scenes. That is one more reason never to size your connection on the displayed average. When a service uses adaptive bitrate (HLS or DASH), the player automatically switches to a lower quality if the connection weakens; when a stream is offered at a single quality, as many MPEG-TS streams are, the player has no way out and the picture freezes. How these protocols work is explained in the article HLS, MPEG-TS and DASH.

The safety margin: why double the stream's bitrate

Having exactly the stream's bitrate is not enough. The speed advertised by your router is a theoretical maximum; usable speed is reduced by several cumulative losses:

• protocol overhead (TCP, IP, HTTPS encryption), which takes a few percent;
• Wi-Fi, which can halve or third the real speed as soon as the device is two rooms from the router;
• evening congestion, at your provider or at the server broadcasting the stream;
• the household's other uses: console updates, photo backups to the cloud, video calls.

A simple, prudent rule is to allow at least 1.5 to 2 times the stream's bitrate for each screen. This margin also lets the player fill its buffer faster than the video is consumed, which absorbs small passing dips.

Working out the need for several screens

Speeds add up. To estimate a household's need, list the uses that can happen at the same time at the busiest hour, generally between 8 pm and 11 pm.

Worked example

Take a family with the following simultaneous uses:

1. a 4K TV in the living room: 20 Mb/s stream;
2. a tablet in a bedroom in Full HD: 6 Mb/s;
3. a phone in HD: 4 Mb/s;
4. browsing, messaging and video calls: about 5 Mb/s.

The total reaches 35 Mb/s. With a 1.5 margin, aim for at least 50 Mb/s actually available in the home, not just stated in the contract. A fiber line at 300 Mb/s or more covers this need very comfortably; an ADSL line at 15 Mb/s, by contrast, will not even allow 4K alone in good conditions.

The special case of ADSL and VDSL

Over copper, speed depends heavily on the line length to the exchange. An ADSL line often tops out between 1 and 15 Mb/s, while a short VDSL2 line can exceed 50 Mb/s. If your provider's TV service also uses this line, it reserves part of the bandwidth. In that case, set your streaming apps to a lower fixed quality (HD rather than Full HD): a slightly less sharp but smooth picture is far more pleasant than a sharp one that freezes every two minutes.

4G and 5G at home

4G or 5G routers sometimes offer high speeds, but very variable depending on the time and the load on the cell. They are also often subject to data caps or fair-use rules. At 9 GB per hour in 4K, an evening of films can add up. Check the terms of your plan before switching all the TVs onto it.

Testing your speed properly

A speed test is only as good as its measurement conditions. Here is a repeatable method.

1. Test from the device that has the problem, not from your phone next to the router. Many TVs and Android boxes offer a browser or a test app; otherwise, test from a computer placed in the same spot.
2. Take a reference measurement over Ethernet, a computer wired directly to the router. If that test is good and the TV's Wi-Fi test is bad, the problem is in the home, not at the provider.
3. Stop other uses during the measurement: downloads, updates, backups.
4. Repeat at different times: once around 10 am, once around 9 pm. A large gap signals saturation at peak hours.
5. Note the three values: download speed, upload speed and latency (ping). Latency and its variation are explained in the article latency, jitter and packet loss.

The limits of a speed test

A test measures speed between your device and a nearby test server, often hosted by your own provider. It says nothing about the path between you and the server actually broadcasting the video. It is therefore entirely possible to get 500 Mb/s on the test and still suffer drops on a particular stream: in that case, the source or its delivery route is at fault. To compare providers or report insufficient service quality in France, the regulator Arcep provides information and a reporting area at arcep.fr (France).

What matters as much as speed

High speed does not guarantee smooth playback. Several elements matter just as much:

• Stability. A steady 30 Mb/s connection beats one that swings between 5 and 200 Mb/s.
• Decoding. A device that does not decode HEVC in hardware will stutter in 4K even on fiber. The symptom looks like a network problem when it is the processor.
• The local link. An old TV whose Ethernet port is limited to 100 Mb/s is more than enough for 4K; on the other hand, a congested 2.4 GHz Wi-Fi may not hold 20 Mb/s. The guide Wi-Fi, Ethernet or powerline compares the options.
• The player's cache. A larger buffer absorbs variations better. A libmpv-based player like AICKO IPTV lets you adjust this behavior; the approach is described in the guide fixing buffering.

Common mistakes

• Buying a faster plan to fix a Wi-Fi problem. If the TV gets 10 Mb/s over Wi-Fi while the router gets 900, changing plan will change nothing.
• Forcing 4K on a Full HD TV. The stream uses two to three times more bandwidth for a picture the screen will scale down anyway.
• Forgetting upload speed when someone is sending large backups: a saturated upload also slows reception, because the TCP acknowledgments no longer get through.

Summary

• Divide Mb/s by 8 to get MB/s; count about 0.45 GB per hour per Mb/s.
• Orders of magnitude: 3 Mb/s for SD, 5 for HD, 8 to 10 for Full HD, 15 to 25 for 4K depending on the codec.
• Allow a margin of 1.5 to 2 times the stream's bitrate, and add up the screens used at the same time.
• Test from the device concerned, then over Ethernet, at several times of day.
• Network stability, Wi-Fi and hardware decoding often weigh more than the plan's headline speed.

Frequently asked questions

Is fiber essential for 4K?

No. A line that steadily delivers 30 to 40 Mb/s to the device is enough for an HEVC 4K stream. Fiber mainly brings margin and stability when several screens run at the same time.

Why does my test show 300 Mb/s while the video drops?

The test measures the route to a nearby server, often at your provider. The drop can come from the room's Wi-Fi, the server broadcasting the stream, decoding too heavy for the device or a large variation in latency. Run the test again from the TV itself, then over Ethernet.

Is 8K worth considering?

8K content is still very rare and its bitrates often exceed 50 Mb/s. For a household, sizing your connection on 4K is today more than enough.

Does lowering the quality really make a difference?

Yes, and an important one: going from 4K to Full HD often divides the bitrate by two or three. On a limited connection, it is the most effective setting for stopping drops.