- Broadband speed is measured in megabits per second (Mbit/s) and gigabits per second (Gbit/s), where 1 Gbit/s equals 1,000 Mbit/s.
- Ofcom classes 30 Mbit/s and above as superfast, 300 Mbit/s and above as ultrafast, and 1 Gbit/s and above as gigabit-capable.
- Download speed measures data coming to the home, while upload speed measures data sent from it; most copper and part-fibre lines are asymmetric.
- Ofcom rules require providers to give a minimum guaranteed speed at the point of sale, with a right to exit if speeds fall persistently below it.
- Actual speeds are often lower than advertised because of contention at peak times, WiFi limits, and line factors, which Ofcom codes of practice address.
Broadband speed is measured in Mbit/s, with 1 Gbit/s equal to 1,000 Mbit/s. Ofcom calls 30 Mbit/s superfast and 1 Gbit/s gigabit. Real speeds are often lower than advertised due to WiFi, contention and line factors.
Last reviewed: June 2026
What Mbps and Gbps mean
Broadband speed describes how much data can move per second. The common unit is the megabit per second, written Mbit/s or Mbps. A gigabit per second, written Gbit/s or Gbps, is 1,000 megabits per second. It is important not to confuse bits with bytes: a megabit is one eighth of a megabyte, which is why a file size in megabytes downloads more slowly than the megabit figure might first suggest. Dividing a connection speed in megabits by eight gives a rough figure in megabytes per second.
The headline number a provider advertises is the download speed, the rate at which data arrives from the internet. This is the figure that matters most for streaming, browsing and downloading, but it is only part of the picture.
Download versus upload
Download speed measures data coming to the home, and upload speed measures data sent from it. Most copper and part-fibre connections are asymmetric, meaning the download speed is much higher than the upload speed. This suited an older pattern of internet use where households mainly received data. Heavier use of video calling, cloud backup and working from home has made upload speed more important, and full fibre can offer symmetric options where upload matches download.
| Tier | Minimum download threshold | Typical technology |
|---|---|---|
| Decent (USO) | 10 Mbit/s download, 1 Mbit/s upload | Any meeting the Universal Service Obligation |
| Superfast | 30 Mbit/s and above | FTTC, SOGEA, cable, full fibre |
| Ultrafast | 300 Mbit/s and above | Full fibre, cable |
| Gigabit-capable | 1 Gbit/s and above | Full fibre, upgraded cable |
Ofcom speed definitions
Ofcom uses defined thresholds to describe broadband tiers, which gives a consistent way to compare connections. A download speed of 30 Mbit/s or more is classed as superfast. A download speed of 300 Mbit/s or more is classed as ultrafast in Ofcom Connected Nations reporting. A connection capable of 1 Gbit/s or more is described as gigabit-capable. These definitions sit behind government targets and the way coverage is measured, even though providers sometimes use the marketing terms more loosely.
Why your real speed is lower than advertised
There are several reasons the speed delivered to a device falls short of the package headline. WiFi is a common culprit, because the wireless link between the router and a device can be much slower than the broadband coming into the home, especially through walls or at distance. Contention is another: providers share network capacity between users, so speeds can dip at peak times in the evening when many people are online at once. Line factors such as the copper distance on FTTC, the device being used, and the number of connected devices all play a part.
To compare like with like, a wired speed test run directly from the router gives a truer picture of the broadband than a WiFi test taken across the home. Ofcom codes of practice require providers to be clear about expected speeds and to give a minimum guaranteed figure at the point of sale.
Minimum guaranteed speed and your rights
Under Ofcom rules, providers that have signed up to the relevant code of practice must give a minimum guaranteed download speed before a contract is agreed. If the speed falls persistently below that figure and the provider cannot fix it within a set period, the customer gains a right to exit the contract without penalty. This protection is designed to address the gap between advertised and delivered speeds.
Matching speed to your needs
The right speed depends on how many people use the connection and what they do. A single user who browses and streams in standard definition needs far less than a busy household with several 4K streams, online gaming and home working at once. Superfast suits many homes, while ultrafast and gigabit give headroom for heavy simultaneous use, particularly on the upload side for video calls and backups.
How to measure your real speed
The most reliable way to see what a line delivers is to run a speed test with a device connected to the router by an Ethernet cable rather than over WiFi. This removes the wireless link as a variable and shows the speed reaching the home. Running the test at different times, including a busy weekday evening, reveals how much the connection dips under contention. Closing other apps and pausing large downloads during the test avoids skewing the result. Ofcom and other tools provide tests, and comparing several readings gives a fairer picture than a single result.
If a wired test sits well below the minimum guaranteed speed and the in-home setup is sound, the issue may lie with the line itself. Reporting this to the provider allows the connection to be investigated and, where the minimum is persistently not met, may open the right to exit the contract without penalty under the Ofcom code of practice.
Speed is only part of the picture
Raw download speed grabs attention, but consistency, upload capacity and latency often matter more in daily use. A connection that holds a steady speed through the evening can feel better than a faster one that collapses under peak load. Likewise, a strong upload speed transforms video calls and backups, and low latency improves gaming and any activity that depends on quick responses. Reading a broadband offer with all of these in mind, rather than the headline number alone, gives a truer sense of how it will perform.
A common source of confusion is the gap between the speed of the line and the speed an individual device records. Even on a fast connection, an older laptop, a distant phone on WiFi or a device with a weak wireless card can report a fraction of the line speed. The connection coming into the home sets the ceiling, but the equipment and the wireless conditions inside the home decide how much of that ceiling each device actually sees. This is why upgrading a package brings little benefit if the bottleneck is really the WiFi or an ageing device, and why diagnosing slow speeds means looking at the whole chain rather than the line alone.
Frequently Asked Questions
What is a good download speed in the UK?
Ofcom classes 30 Mbit/s and above as superfast, which suits many households. Larger homes with multiple simultaneous users, 4K streaming or home working benefit from ultrafast connections of 300 Mbit/s or more. The right figure depends on how many people use the connection at peak times.
What is the difference between Mbps and MBps?
Mbps means megabits per second and is how broadband speed is advertised. MBps, with a capital B, means megabytes per second and is often how file transfers are shown. One byte is eight bits, so dividing a speed in megabits by eight gives the rough figure in megabytes per second.
Why is my actual speed lower than advertised?
Common reasons include WiFi limits between the router and a device, contention at peak times when the network is busy, the copper distance on part-fibre lines, and the age of the device. A wired speed test from the router gives a truer picture than a WiFi test across the home.
What speed do I need for 4K streaming?
A single 4K stream typically needs a steady connection of around 25 Mbit/s, though requirements vary by service and codec. For several simultaneous 4K streams, a superfast or ultrafast connection provides headroom so that other activity does not cause buffering.
What is the average UK broadband speed?
Ofcom measures average UK broadband speeds in its regular reporting, and the figure has risen over time as full fibre has spread. Averages differ between urban and rural areas, and Ofcom Connected Nations data sets out the current position by connection type.
