There are now three different sizes of SIM you might need to use, depending on your device: a standard SIM, micro-SIM or nano-SIM. We'll send you the right SIM for your phone when you take out your contract or upgrade with us.
If you're using a device that you didn't get from us, you may not have the right sized SIM for your device to work. If you don't, you'll need to visit a 3Store to get the correct SIM or an adapter. Find out more about SIM adapters and how to use them here.
The standard SIM is the most commonly used SIM in phones. It's around two and a half centimetres long, and one and a half centimetres wide.
The micro-SIM is a smaller type of SIM that was first used in the iPhone 4. It's about half the length of the standard SIM. Many other phones also use micro-SIMs.
A nano-SIM is around 40% smaller than a micro-SIM. You'll need a nano-SIM if you're using iPhone 5, and you can get one by going to a 3Store or by calling us.
*Calls cost 5.1p per minute from a BT landline, other networks may vary.
To find out what kind of SIM your device needs, check its manual by visiting our device support.