ADSL broadband is delivered through your phone line to your home – and the journey starts at your local telephone exchange. Find out about each stage of the journey, and how it affects your broadband speed.
Understanding your
broadband speed
Find out about broadband speed
– across the UK, in your area
and in your home.
Broadband in the UK
The choice of broadband you can have depends on where you live in the UK. Use our availability checker to find out the types of broadband available in your area – and what the plans are for the future.
Broadband to your home
ADSL broadband is the most common type of broadband, it is delivered through your phone line to your home – and the journey starts at your local telephone exchange. Find out how broadband gets to your home, and how its journey affects the speed you get.
Broadband at home
You can help speed up your broadband by making sure everything is working as well as it can in your home. Use our checklist to make sure you get the fastest connection possible.
Broadband in the UK
Find out about broadband in the UK and plans for your local area
Depending on where you live in the country, there are different types of broadband connection you can get.
Broadband through your phone line
Also known as ADSL or ADSL2+ it's the most widely available type of broadband – available to over 99% of homes in the UK. It's delivered to your home over the BT phone network from your local telephone exchange.
Cable broadband
The underground cables that carry cable broadband were first installed in the UK in the early 1990s. Cable broadband is available in some – mainly urban – areas of the UK, but isn't as widely available as ADSL broadband through your phone line.
Super-fast fibre optic broadband
Fibre optic broadband is the most up-to-date broadband available, giving you a more powerful, up to 76Mbps connection to the internet through the latest generation fibre-optic cable. Use our Infinity availability checker to see if superfast fibre optic broadband is coming to your area.
More on broadband in the UK
How do I choose the best type of broadband for me?
ADSL broadband is the most widely available and widely used broadband in the UK, with 99% of homes able to get it. You may also be able to get BT Infinity super-fast fibre optic broadband in your area. Check the map above to find out when fibre is coming to your region.
Satellite broadband is also available in the very small number of areas where ADSL broadband isn't available due to distance from the telephone exchange or other factors. Satellite broadband is used mainly for general internet access and browsing.
How much speed do I need?
Broadband speed is the rate at which information is sent (up-stream, or upload speed) or received (down-stream, or download speed) on your broadband line. As most people tend to receive more information than they send, broadband services are usually set up with much higher download speeds than upload speeds.
Note that a slower speed doesn't stop you from doing things online – but it may make some things take a bit longer.
Broadband speed is measured in 'Mbps' – which stands for 'megabits per second'. The more megabits per second, the faster your connection speed. To give you an idea of how long it takes to do the same job at different speeds, look at the table below.
Activity |
File size |
16Mbps |
8Mbps |
4Mbps |
4KB |
0.2 seconds |
0.4 seconds |
0.8 seconds |
|
Photo |
1MB |
0.5 seconds |
1 second |
2 seconds |
Music track |
4MB |
2 seconds |
4 seconds |
8 seconds |
Film |
225MB |
2 minutes |
4 minutes |
8 minutes |
The file sizes above are in MBs – megabytes – which is a unit of measurement for computer files. The more megabytes a file has, the 'bigger' it is, and the more space it takes up on your computer – therefore it will also take longer to download from the internet.
How do I test my broadband speed?
If you already have BT Broadband or BT Infinity and want to check your line rate or throughput speed
You can check your current broadband line rate or throughput speed with our online speed checker.
If you don't already have broadband
Use our broadband speed test to check the broadband speed you're likely to get.
Broadband to your home
1. Your local telephone exchange
The main factor affecting your broadband speed is the distance from your telephone exchange to your home. Generally speaking, the closer you live to the telephone exchange, the higher the broadband speed your phone line can support, although line routing is not always 'as the crow flies'. There are other things that can affect the broadband speed you receive, but this is by far the most important factor.
This is true of every ADSL broadband provider, as they all provide broadband to your home from your local telephone exchange.
Some broadband providers manage broadband traffic at the telephone exchange – which can have an effect on your speed. Find out more about traffic management below.
2. Once broadband leaves your exchange
Your broadband speed is affected by the number of other people using the network at the same time, so it's important you test your broadband speed at different times of the day to see how other users will affect your speed. More people sharing broadband connections at peak times means congestion in broadband traffic, which in turn can mean slower speeds – particularly during the peak usage time of 5pm – midnight.
3. Your local cabinet
A cabinet is a small, usually green, box you can see on street corners throughout the country. These are all maintained by BT along with telephone exchanges, and are another connection point for your phone line between the local telephone exchange and your home, but on a more local level.
4. The cabinet to your home
The final stage of the broadband journey is from the cabinet to your home. While this distance isn't as critical to your broadband speed as the overall distance from the telephone exchange to your home, it still has an effect on your speed.
Remember that the time of day you're online can also affect your speed – the more users that are online at the same time as you, the slower your speed will be.
More on bringing broadband to you
What is traffic management?
Broadband traffic management is when a broadband provider puts limits on the speed people can get over their broadband connection. This can happen when there is a large demand for broadband at the same time in the same area, or when one user has used a large amount of data usage, so their broadband speed is artificially slowed temporarily. Traffic management can be done in two ways: either as part of the service you receive, or to manage heavy usage by some customers.
At BT, we always aim to get broadband to you as fast as possible, so before broadband leaves the telephone exchange we monitor how much internet traffic there is on the network and manage it to make sure everyone gets the best speed possible.
You can think of it like this: imagine you're in a car on a motorway. Heavy internet users are flooding many more cars on to the motorway, making it more difficult for you to move around.
Traffic management makes sure that all users get their fair space on the road – or the best speed possible.
How does BT manage broadband traffic?
We're constantly investing in the telephone network to make sure everyone gets the best speed possible.
We believe it's important that all of our customers receive an optimal service whether they only use the internet a small amount or whether they are very heavy users of the internet. That is why we operate a traffic management policy to protect the experience of the majority of our customers during peak times:
The traffic management policy only affects a tiny minority of customers. Latest information shows 99.9% of all BT Broadband customers weren't impacted at all
Traffic management is only applied during the peak period of the day when the very heavy usage could impact others. During the rest of the day all customers are free to use as much as they like
The policy only affects customers with exceptional broadband usage – for example, you could watch the standard size BBC iPlayer video every second of every day and still not be impacted by the very heavy user traffic management policy
We also control non time-critical, 'peer to peer' traffic during the peak period so that critical services like video streaming aren't affected. Again outside of the peak period all customers are free to use as much 'peer to peer' services as they like
Find out more about our Traffic Management Policy here.
Why does the time of day affect my broadband speed?
The actual speeds you will experience will differ and will continually vary throughout the day as levels of congestion on the internet change. You should not expect full speeds all the time, especially during the daily peak period (5pm-12 midnight) when global internet speeds are at their slowest due to congestion.
The main factors governing the day-to-day download speed you will experience over your line are:
The time of day i.e. how busy the network and the internet are (6–9pm being the busiest time, when speed can reduce significantly)
The speed of individual websites you are visiting (some have a maximum access speed)
Whether you're sharing your connection with others in your home
Whether you have software running in the background, such as spyware
Broadband at home
If you already have broadband, it's worth taking a few moments to make sure it's working at its fastest in your home. If you're thinking of getting broadband, use our checklist to make sure you get the best connection.
If you identify the activities that don't have to be carried out at peak times and instead do them at different times of day, you'll be able to share your connection better between your home users and the rest of the online community.
1. Interference from wiring
Interference on your broadband line is similar to when you put a mobile phone near a speaker and it makes a static noise – radio and electrical devices have a similar effect on a broadband line and can stop it working properly.
You can reduce interference by making sure your home has the most up-to-date master phone socket possible – particularly if you use extension wiring. If you're a BT Broadband customer, you can also fit a BT Broadband Accelerator to reduce interference on your line.
2. Microfilters not used properly
Any equipment like phones, faxes and digital TV boxes can introduce interference to your broadband line, but fitting ADSL microfilters to all the sockets in your home will reduce this. You can get microfilters from most High Street electrical shops.
You need a microfilter for every telephone socket in your home that has equipment plugged in. (It's recommended you have a maximum of four extension sockets with microfilters attached for each telephone line you have.) Equipment that needs a microfilter includes:
Broadband modem or router
Telephones
Answering machines
Digital TV boxes
Fax machines
Alarm systems
Plugging in your microfilters
At each phone socket where a device plugs in:
-
Unplug the device from the socket
-
Plug a microfilter into the socket
-
Plug the device you have just unplugged into the microfilter's phone socket, and plug your broadband equipment into the computer's socket. The microfilter will usually have a diagram on it to show you which socket is which
3. Not using the main phone socket
Your broadband service works best when there's the shortest possible distance between the BT phone exchange and your broadband router, so make sure you plug your broadband router into the main phone socket in your home.
4. Out of date wireless router
If you have upgraded to a faster broadband service but still have an old wireless router, it may not be able to provide the broadband signal as fast as a more up to date router.
There are broadly three types of wireless router:
Wireless-B routers can support speeds of around 5-6Mbps
Wireless-G routers can support speeds of around 20Mbps
Wireless-N routers can support speeds of around 100Mbps
If you check your router, you may find you aren't using the most up to date way of connecting to broadband.
Please note – the wireless Mbps speeds quoted are maximums and the layout of your home and distance of your PC from your wireless router will affect actual performance.
5. Wireless interference
If you're using wireless broadband in your home, make sure you place your broadband router away from barriers that may block the signal, including thick walls or ceilings, large metallic surfaces such as radiators, mirrors and refrigerators. Wireless works best when there's a clear space to your computer.
Although a wireless connection gives you more flexibility to position your devices around your home, it can occasionally suffer from interference, which can affect your internet browsing. An Ethernet cable is generally not affected by interference so may give you a faster, more reliable connection. And if you use a USB cable to connect your computer to your router, the speed of the connection can be affected by other USB devices, such as your keyboard, mouse and webcam all using USB at the same time.
6. Other users in your home
If you have more than one device using your broadband connection at home, your speed could be affected. The more devices you connect to your broadband at the same time, the more your speed will be impacted.
Other devices that can affect your broadband speed include other computers and games consoles.
7. Using an old computer
If you have an old computer, this can affect your internet experience even if you have a fast broadband speed.
If your computer is less than 5 years old, then it probably supports the maximum broadband speed you can receive. It's worth checking your computer meets any minimum requirements your broadband provider specifies in their small print. If your computer is too old and slow, it may be unsuited to a broadband connection, so a newer computer may be necessary.
8. Using old software
If you're using an old operating system, such as Windows 95, then this will significantly affect your broadband speed.
If your computer runs slowly, it may make your internet experience feel slower. You can help avoid this with regular maintenance by regularly running virus scans, deleting your browser cookies and clearing your browser history. Just turning off your computer for five minutes if it's left on for a long time can help by closing down some background tasks your computer may be performing.
And if you have a newer computer that runs slowly, it may make your internet experience feel slower. You can help avoid this with regular maintenance of your computer, for example by regularly running virus scans, deleting cookies and clearing your browser history.
Check you have the latest version of your internet browser software installed – older versions might not be able to handle all of the types of content on newer websites, and can cause pages to download slowly.
9. Surfing at peak hours
The actual speeds you will experience will differ and will continually vary throughout the day as levels of congestion on the internet change. You should not expect full speeds all the time, especially during the daily peak period (5pm – 12 midnight) when global internet speeds are at their slowest due to congestion.
By identifying the internet activities that don't have to be carried out at peak times and doing them at different times of day, you'll be able to share your connection better between your home users and the rest of the online community.
Here's an example of what you can do: spread out activities that involve downloading large files so that they don't tie up your computer and broadband connection when you want to use the internet. For example, if you or someone in your household uses peer-to-peer software (which continuously downloads and uploads files to be shared with other internet users), check the help section of your software to turn it off at times when other people at home want to use the internet.
More on broadband speed in your home
Want more help with improving your broadband speed?
Once you've followed our tips, there are several other ways you can help boost your broadband speed:
Test your speed and get personalised help to improve it.
We'll take you through a step-by-step guide to maximising your broadband speed.
If you're a BT Total Broadband customer, get a BT Broadband Accelerator
If you have broadband with us, and you have extension wiring at home, you may find a BT Broadband Accelerator improves your broadband speed.
Why is my 'upload' speed slower than my 'download' speed?
While your home set-up is important, the starting point is to understand the quality and speed of the broadband line coming into your home, as this can have a big effect on your overall broadband experience.
Broadband speed is the rate at which information is sent (up-stream, or upload speed) or received (down-stream, or download speed) on your broadband line. As most people tend to receive more information than they send, broadband services are usually set up with much higher download speeds than upload speeds.
Your download speed will typically be faster than your upload speed, as the vast majority of people receive more information on the internet than they 'push out' to other internet users.
How can I improve my wireless broadband connection?
There are several simple steps you can take to improve your wireless performance:
Most wireless problems are due to interference from other networks or appliances. You can try to avoid interference by changing the wireless channel used by your router. You will need to consult the userguide you received with your wireless router to do this. Once you've changed your wireless channel:
Wait for 60 seconds each time after changing the channel to check whether the signal has improved
Because conditions vary, there is no easy way to find the best channel other than trial and error
If there's an antenna on your router and wireless adapter, make sure it's pointing upwards
Put the router in a central place in the house (where telephone sockets allow)
Place the router on a table, shelf, or other surface, not on the floor
If you can, use cables or an antenna extension so your computer's wireless adapter is away from the computer and other interference
Move all wireless devices away from possible sources of interference such as microwave ovens, metal sheets, cordless phones, cordless keyboards and mice, video senders, etc. Switch them off or move them away to identify which ones cause interference
Some devices, such as video senders, let you change their operation channel. If they're causing problems, try switching them to a different channel.
Interference might happen at different times (for example, if a video sender is only used in the evening, or when a microwave oven is being used). This means you might need to check electrical devices that are only used at certain times.
Some laptops with a built-in wireless adapter have a lower wireless performance than an external wireless adapter such as a USB dongle. If you're worried about this you can upgrade to a USB wireless adapter or try to borrow one for testing
The new BT Home Hub automatically changes wireless channels if it detects interference, helping keep your connection as strong as possible.
Broadband speed FAQs
Got a question about broadband speed? Find the answer here.
How does the broadband speed checker work?
Because there are different factors that can affect your broadband speed, our broadband speed checker personalises the results to your phone line, taking into account how far you are from your telephone exchange and the way your phone line is routed to your home.
We'll always give you the best broadband speed available to you, so if you can get BT Infinity super-fast fibre broadband, we'll show this as the fastest speed available to you, with BT Total Broadband speed over your normal copper phone line shown below.
If BT Infinity is not yet in your local area, we'll give you a speed estimate for up to 16Mb BT Total Broadband. We will display the line speed we think you are likely to get, along with a range which confirms where your actual speed will fall once installed. This is typically within a maximum of 1-2Mb of your estimated speed.
These estimates are calculated by comparing your line with similar lines across the UK and measuring the typical speed that these lines get for their broadband service.
It can take up to three days for your line to stabilise once your broadband has been setup, so you will only know the actual speed that you're getting after this period. This is why we give you an estimated speed and the range that the actual speed will fall within.
If after three days, the speed you're getting is considerably lower than the speed range we estimated for you, please see our tips on how you can make simple changes to improve your broadband speed.
How do I test my broadband speed?
If you already have BT Broadband or BT Infinity and want to check your line rate or throughput speed
You can check your current broadband line rate or throughput speed with our online speed checker.
If you don't already have broadband
Use our broadband speed test to check the broadband speed you're likely to get.
Why are broadband speeds often different from those advertised?
Most broadband speeds are advertised as being 'up to' a specific number of Mbps. This gives you a good idea of the maximum speed you can possibly get. Before you buy broadband, you are usually encouraged to take a broadband speed test to find out what your likely speed will be, so you get a good idea of your likely broadband speed before you buy broadband.
Some broadband providers are encouraging the advertising of 'average' broadband speeds, but this isn't as useful as an 'up to' measure because it doesn't give an accurate view of what speed is available to you specifically – and the actual broadband speed you get may be very different to the 'average' speed you're given.
At BT, we aim to predict your broadband speed to within 1Mb either side of the speed you will get. If we detect that your line isn't operating to its predicted speed after you've bought broadband from us, we'll take steps to fix the issues and help you get the best possible speed on your line.
I don't understand some of the data from my broadband speed test
If you already have broadband and you've tested the speed of your line, you may see lots of different results. Here's an explanation of what some of the terms mean:
DSL Connection Rate
This shows the top speed between your broadband router and your local exchange. This is usually the maximum speed your line can support for the product you're on, e.g. the maximum speed up to 8Mb. The factors that can affect this speed are the length and quality of your phone line from the exchange to your broadband router, including the wiring in your home.
IP Profile for your line
This is the maximum speed at which 'internet' traffic is actually allowed to travel over your line. It's automatically set by the broadband network to give you the most reliable and stable broadband speed for your line conditions. Your IP profile automatically adjusts, based on the way your line performs, so may be lower than your DSL connection rate to protect your online experience. When you make changes to improve your speed, e.g. reducing interference from wiring in your home, your connection rate may change straight away, but it can take several days for the adjustments to show against your IP profile.
Download speed
This is the actual speed of your line at the time you ran the test. Your 'Download speed' and your 'IP profile' will probably be different. There are lots of reasons for this, such as the number of people in your home using the broadband line at the same time, how busy the internet is and whether your computer is doing other things, e.g. if other software or programs are running. Your Download speed will vary throughout the day and tends to be lower at peak times, when lots of people are using the internet.
What is super-fast fibre optic broadband?
Fibre optic broadband uses the latest broadband technology to provide a much faster and more powerful internet connection, typically offering download speeds of up to 76Mb a second – roughly twice the maximum speed of standard (ADSL) broadband over your phone line.
Super-fast fibre optic broadband can give you:
Faster surfing – improved browsing and smoother video streaming.
Faster downloads – download large files in much less time.
Faster uploads – send large emails and upload photos more quickly.
Improved multiple user experience – do more online, faster, at the same time.
'Up to 76Mb' will give you enough speed to run multiple bandwidth-hungry applications at home. For example, you could be watching different HD movies, while others in your household are gaming or working on complex graphics or video projects.
How do other people using the network affect me?
Your broadband speed will vary depending on the time of day you're online. During the peak traffic period (5pm – 12 midnight) your speed will normally be slower, as this is the time when global internet speeds are at their slowest due to congestion – i.e. this is the time when the amount of people using the internet at the same time is at its highest.
By identifying the internet activities that don't have to be carried out at peak times and doing them at different times of day, you'll be able to share your connection better between your home users and the rest of the online community.
You could try doing activities that involve downloading large files at different times so they don't tie up your broadband connection when you want to use the internet.
Can I improve my speed by connecting with an Ethernet cable?
Although a wireless connection gives you more flexibility to position your devices around your home, it can occasionally suffer from interference, which can affect your internet browsing. An Ethernet cable is generally not affected by interference so will give you a faster, more reliable connection. And if you use a USB cable to connect your computer to your router, the speed of the connection can be affected by other USB devices, such as your keyboard, mouse and webcam all using USB at the same time.
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