When your phone or computer uses the internet it sends and receives email, digital video, music and photographs as data

Some apps use data, such as when you use Google Maps, or when you make changes to a shared calendar that is synced online.

[Read more: What is data roaming? Tips for using your phone abroad]

You tend to use data fairly often when using a computer or mobile phone, and your broadband or mobile contracts typically allow you to use a certain amount of data per month (known as your data allowance), some broadband contracts allow unlimited data use.

How much data can I use?

Data is measured in kilobytes (KB), megabytes (MB) and gigabytes (GB). There are 1,024 KB in 1 MB and 1,024 MB in 1 GB.

Broadband providers and mobile phone providers give you a monthly data usage limit as part of your contract, unless you are on an unlimited data contract.

Exceed your data allowance each month and you’ll be charged extra - unless you have unlimited broadband. Go over your BT broadband allowance and BT charges £1.80 per GB or part of.

How much data do I need?

The amount of data you use depends on what you’re doing and how much time you spend doing it.

Sending an email or using an IM service like WhatsApp Messenger uses relatively little data, downloading a music track uses a moderate amount, and streaming or downloading a HD movie uses the most.

Here are some examples of data use:

High definition movie (2 hours)

4.2 GB

Standard definition movie (2 hours)

1.9 GB

Online catch-up TV service (1 hour)

644 MB

Video streaming: for example, YouTube (1 hour)

429 MB

Online gaming (1 hour)

43 MB

Music (1 album, 10 tracks)

80 MB

Broadband data

BT data is usually measured in GB. BT, like other broadband providers, offers packages with different data allowances, so you can work out roughly what you can do with each allowance.

Broadband product




Broadband (15GB)
Broadband Plus (15GB)
BT Total Broadband Option 1 (15GB)
Broadband (15GB)
15GB Broadband

1 hour a day of web browsing

1 hour a week of online TV

1 HD film a month, 100 music tracks/10 albums, 100 photo uploads a month

30GB BT Infinity Lite
30GB BT Infinity 1

2 hours a day of web browsing

2 hours a week of online TV, 3 hours a week of video streaming (eg YouTube), 2 hours a week of online gaming

2 HD films a month, 200 music tracks/20 albums a month, 200 photo uploads a month

Infinity 1 (50GB)
Infinity 1 Plus (50GB)
BT Infinity 1 (50GB)
BT Total Broadband Option 2 (50GB)
50GB BT Infinity Lite
50GB BT Infinity
50GB BT Infinity 1

4 hours a day of web browsing

5 hours a week of online TV, 5 hours a week of video streaming (eg YouTube), 5 hours a week of online gaming

3 HD films a month, 400 music tracks/40 albums a month, 400 photo uploads a month

Any "Unlimited" Broadband or Infinity product 
BT Total Broadband Option 3 
BT Infinity Option 2


Unlimited browsing

Unlimited online TV, unlimited video streaming, unlimited online gaming

Unlimited films, unlimited music tracks/albums, unlimited photo uploads

Mobile phone data

Mobile phone data is typically measured in MB and GB.  Networks offer a range of tariffs with different data allowances. BT Mobile has three packages offering 500MB, 2GB and 15GB of data.

If you have a 4G SIM and mobile phone you should ensure the data allowance is higher than normal. 4G doesn’t use more data than 3G, but because it’s faster than 3G, streaming HD video more smoothly, you may find you use your phone for things that use more data.

[Read more: What is 4G]

How do I know how much broadband or mobile data I’ve used?

Most companies enable you to check your data usage by looking at your account details online, or by calling their customer service number.

BT Broadband customers can log on to www.bt.com/mybt to view data use and check how much is remaining. Go to My Bill – View your recent usage. Click the Broadband tab and View your broadband usage.

The My BT app (Android and iOS) allows BT Broadband customers on a limited broadband usage limit to check download and upload use and see exactly what is using up their data allowance.

Read more in our article: Discover the easy way to manage your BT account with the My BT app.

The majority of mobile phone providers have smartphone apps or web-based portals that show you how much data you have used.

BT Mobile customers can log in to www.bt.com/mymobile to see a detailed view of usage.

In addition the free BT Mobile smartphone app (Android and iOS) lets you see how much data you have left.

If you find yourself regularly using more data per month than your allowance, talk to your broadband or mobile provider about moving to a contract with a bigger or unlimited data allowance.

Alternatively try to reduce the amount of data you use.

How can I use less data on my home broadband and mobile phone?

1: Download cautiously

Be careful about the things you use your computer or mobile phone for.  

Broadband users without an unlimited allowance should take care when downloading large files such as movies or TV series, particularly if they are in high definition. HD files are bigger and use more data.

Mobile phone users should watch out if streaming video using BBC iPlayer or music using Spotify and YouTube.

2: Use wi-fi

Connect your mobile phone to wi-fi hotspots when out and about to go online without using data.

BT Broadband and BT Mobile customers get free access to 5 million hotspots via the BT Wi-fi app for Android,  Apple and Windows Phone.  Read more in our guide: How to use the BT Wi-fi app.

3: Turn off push email

Push email is when emails are sent directly to your phone from the server. It means you are constantly in touch, but uses data each time the email is ‘pushed’.

4: Deactivate automatic app refresh

Many apps are updated frequently and if you aren’t careful, will update in the background and use data without you realising.             

Android: Launch the Google Play Store. Go to Menu – Settings. Look for Auto-update apps and choose Auto-update apps over wi-fi only.

iPhone: Discover where to find Background App Refresh.

What about using data abroad on your mobile phone?

When you leave the UK you are no longer connected to your home network, and you will be charged for all data usage. This is known as ‘data roaming’ because you are roaming away from your network.

BT Mobile has just launched Roam Like Home which lets you use your monthly data, calls and text allowance in 47 EU destinations*. This means you can talk, send texts and use the internet without worrying about facing a hefty bill when you come home.  

Go over your allowance and you'll be charged at BT Mobile's standard rate.

Roam Like Home doesn't cover using your phone in non-European countries like Japan, Australia and Canada.

How to turn data roaming off

If in doubt, turn off data roaming on your smartphone. Most phones have it switched off by default, but double check the settings when abroad to make sure your phone is not capable of accessing the internet via the network connection. You can still use wi-fi.

  • Android: Tap Settings - Wireless & Networks, go to More – Mobile networks and turn ‘Data roaming’ off.
  • The interface on Android devices varies between handset manufacturers, so if you can’t find it, check the manufacturer’s website.
  • iPhone: Discover how to turn off roaming here. The screenshots refer to a US device, so look for ‘Mobile Data’ instead of cellular.
  • Windows Phone: Swipe left to get to the Applications List. Tap Settings - Mobile Network, look for the Data Roaming Options box and select Don't Roam.

If you are heading abroad and plan on using your mobile phone, check out our article: How to prepare your smartphone for holiday.

Read more: Free wi-fi, nuisance call block and more - 7 brilliant extras BT customers can enjoy

*Roaming Zone 1a: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Isle of Man, Italy, Latvia, Lithuania, Luxembourg, Malta, Monaco, Netherlands, Poland, Portugal (Incl. Azores & Madeira), Romania, Slovakia, Slovenia, Spain, Sweden, Vatican City. Roaming Zone 1b: Canary Islands, French Guiana, Gibraltar, Guadeloupe, Guernsey, Iceland, Jersey, Liechtenstein, Martinique, Mayotte, Norway, Reunion, Saint Barthelemy, Saint Martin, San Marino, Switzerland