The short answer: broadband speed is measured in Mbps (megabits per second). 100 Mbps means you can download 100 megabits of data every second. That is about 12.5 megabytes (MB) per second, or roughly 7 minutes to download a 5 GB HD film. Download speed matters for streaming and browsing; upload speed matters for video calls and sharing files.
Mbps vs MB/s: the confusing bit
Broadband speeds are measured in megabits per second (Mbps). File sizes and storage are measured in megabytes (MB) and gigabytes (GB). The difference matters because there are 8 bits in a byte.
To convert Mbps to MB/s, divide by 8:
- 100 Mbps = 12.5 MB/s
- 50 Mbps = 6.25 MB/s
- 10 Mbps = 1.25 MB/s
So if you have a 100 Mbps connection and download a 5 GB (5,000 MB) file, the theoretical download time is 5,000 ÷ 12.5 = 400 seconds, or about 6.5 minutes. In practice it takes a little longer due to overheads, but that is the ballpark.
Download speed
Download speed is how fast data comes from the internet to your device. It affects:
- How quickly videos buffer and start playing
- How long downloads take (apps, games, files)
- How smoothly multiple devices work simultaneously
- How quickly web pages load
This is the number prominently advertised on broadband deals ("up to 80 Mbps", "500 Mbps fibre", etc.).
Upload speed
Upload speed is how fast data goes from your device to the internet. It affects:
- Video call quality (your camera and microphone data is uploaded)
- How long it takes to send large files or email attachments
- Cloud backup and storage sync speed
- Streaming or recording if you use a platform like Twitch
On ADSL, upload speeds are typically 0.5–2 Mbps. On FTTC, 10–20 Mbps. On full fibre, 50–500 Mbps. For most people, ADSL upload is the main bottleneck. A 1 Mbps upload makes video calls unreliable.
Latency (ping)
Latency is measured in milliseconds (ms) and represents how long it takes for data to travel from your device to a server and back. Low latency means fast response; high latency means noticeable delay.
- Under 20ms: excellent, unnoticeable in any use case
- 20–50ms: good, fine for gaming and calls
- 50–100ms: acceptable for most uses, may cause slight lag in competitive gaming
- 100ms+: noticeable delay in calls and games; common on satellite broadband
Most fixed-line broadband achieves 10–30ms to UK servers. Latency matters most for online gaming and real-time video calls. For streaming and browsing, it has almost no effect.
What does "up to" mean on a broadband deal?
When a deal advertises "up to 80 Mbps", the "up to" is doing a lot of work. Under Ofcom's Advertising Standards rules, the speed advertised must be achievable by at least 50% of customers at peak times (8–10pm). The other 50% may get less.
When you order, providers are now required to give you a personalised speed estimate for your specific address. This is a better guide than the advertised headline figure. For FTTC especially, your actual speed depends heavily on your distance from the street cabinet.
Mbps vs Gbps
Gbps stands for gigabits per second. 1 Gbps = 1,000 Mbps. Gigabit broadband means your theoretical maximum download speed is 1,000 Mbps (125 MB/s). In practice, real-world speeds on gigabit connections are typically 900–950 Mbps.
Gigabit broadband is available on most full fibre networks for around £30–45/month in 2026. Whether you need it is a separate question. See our guide on what broadband speed you actually need.
Contention ratio
Your broadband connection is shared with other households in your area, particularly on the backhaul between your local exchange and the wider internet. The contention ratio refers to how many users share a given capacity. A lower ratio means less congestion. Most residential broadband has a contention ratio of around 50:1, meaning up to 50 households share the same capacity at the exchange.
This is why speeds often dip in the evenings when everyone is online simultaneously. Business broadband typically has lower contention ratios and guaranteed minimum speeds, which is why it costs more.
Frequently asked questions
Why is my speed test result slower than what I am paying for?
Several factors: the speed test server location, your device's Wi-Fi connection (Wi-Fi is slower than wired), background processes on your device, and time of day (peak hours are slower). For the most accurate result, run a speed test on a device connected to your router via ethernet cable, at off-peak times (midday on a weekday).
What is a good broadband speed in 2026?
The UK median fixed broadband download speed is 69 Mbps (Ofcom Connected Nations 2026). Ofcom's definition of a "decent" broadband connection is 10 Mbps download and 1 Mbps upload. For a modern household, 50–100 Mbps is a comfortable working speed.
Does having more devices slow my broadband?
Only when those devices are actively using bandwidth. A smartphone on Wi-Fi but idle uses almost nothing. The issue is when multiple devices download or stream at the same time. The total bandwidth available is shared across all active devices.