Broadband speed: What is it and how does it work?

Fibre optic, copper, throughput speeds, ADSL and more. If you're confused by broadband terms, we can help.

Fibre optic, copper, throughput speeds, ADSL and more. If you're confused by broadband terms, we can help.

Broadband is something that millions of us use every day on our laptops, tablets and phones to stay in touch, work and play. Broadband speeds vary depending on many factors, including the technology and your location. Let's take a closer look.

What is sync speed?

Sync speed is the speed between your BT Hub and your local telephone exchange. It's sometimes called 'line rate'. Sync speed can depend on the distance from the cabinet or exchange and whether microfilters are installed correctly.

What is throughput speed?

Throughput speed is the speed at which your broadband can actually send and receive data between the internet and your BT Hub. It's what you experience at home when using your broadband connection. It can't be higher than the sync speed. It can vary throughout the day and can be slower during busy periods, especially between 8-10pm. This is the equivalent of the internet rush hour when lots of people are using the shared parts across the network at the same time.

If you run our speed tests in the Troubleshooter or My BT app, we'll show the throughput speeds to your BT Hub.

This may be different to the speed you receive on your device, which is affected by a wide range of factors. Things like the number of devices connected to your Hub at the same time and whether you're using wi-fi or a wired connection.

To see what broadband speeds you can get see Test your BT Broadband speed >

How are broadband speeds measured?

Broadband speeds are measured in megabits per second or Mbps. Each megabit is made up of 1,000,000 bits or 1,000 kilobits. The more megabits, the faster your broadband.

Faster broadband speeds means faster downloads. You can download music and movies quicker, stream from services like Netflix without waiting, and make video calls more smoothly.

The table below shows the minimum broadband speeds you need for some common activities.


Minimum broadband speed needed

Web browsing 1 Mbps (download)
HD video streaming 5 Mbps (download)
Ultra HD video streaming 30 Mbps (download)
Voice over IP 256Kbps (download and upload)
Real time online gaming 256Kbps (download) and 512Kbps (upload)
Video calling 1 Mbps (download and upload)

How do broadband speeds work?

Broadband typically comes into your home through your telephone line. There are two main types of cable for doing this - copper or fibre optic - with different connection speeds.

  • Copper: This is used to deliver ADSL and ADSL2+ broadband from the telephone exchange to your house. The longer the length of copper, the weaker the signal strength and the slower your broadband line will have to operate
  • Fibre optic broadband: Faster than copper, speedy fibre optical cables run from the telephone exchange to the street cabinets. Copper cables are then used to connect a cabinet to your house. This is called Fibre to the Cabinet (FTTC). The maximum broadband speed you get depends on the distance from your house to the cabinet. The closer you are from cabinet to home, the faster your broadband. With Fibre to the Home (FTTH) your maximum broadband speed isn’t dependent on distance as a fibre cable is connected all the way to your house

Fibre to the cabinet route:

Fibre to the cabinet route


Which BT Broadband option is right for me?


We have three types of broadband: Ultrafast Fibre, Superfast Fibre and standard Broadband

Order Ultrafast Fibre, Superfast Fibre or Broadband >

Ultrafast Fibre 250 gives you an ultrafast fibre optic broadband connection with average speeds of 300Mbps.

Whatever you're streaming, downloading or watching, Ultrafast Fibre 250 has the speed you need to connect with the things you care about. Enjoy high quality video calls with friends and family, with less buffering worries; stream your favourite 4K shows on multiple devices - perfect for busy homes; download HD movies and boxsets faster than ever; and upload videos and high-res phots like there's nothing to it.

Superfast Fibre 2 gives you a superfast fibre optic broadband connection with average speeds of 67Mbps.

This means you can all get online at the same time. It's great for downloading or streaming movies, TV shows and music. You can watch iPlayer with less interruption and HD video with less buffering.

If you can't get Superfast Fibre or Ultrafast Fibre or you live in a home with lighter internet usage and fewer devices, standard Broadband is ideal for you. It's perfect for everyday browsing, sending emails and updating your favourite social media sites.

How can I improve my broadband speeds?

If your broadband seems slower than it usually is, check out

Five steps to improve slow BT Broadband speeds >

Upgrade your broadband and discover more about BT Broadband >

Traffic management and fair usage policy

At busy times, internet providers can slow down traffic on the network. This is called ‘traffic management’ and it’s a way of making sure you get the best possible service. And fair usage policies are designed to stop a small number of users from monopolising the traffic at an exchange by slowing them down if they go over a certain usage cap.

We’re proud to say that our broadband packages don’t have any speed restrictions. So you don't need to worry about us slowing you down, even at peak times.


For more information, see BT's approach to broadband traffic management >

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