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Which SIM Card Do I Need?

10 July 2019

When getting a new phone, it can be hard to keep track of which SIM card is which. We've kept everything in this quick blog as simple as possible, so you can find the right SIM card for your phone and aren't left asking: Which SIM Card Do I Need?

What Is a SIM?

A SIM card is a key piece of technology to connect your phone to the world. It stores all sorts of important information, such as the identity of the user, their location, phone number, network authorisation data, personal security keys and depending on phone settings other information such as contact lists and text messages. You can think of the SIM as being like your phone's soul: it is where all the most important information in your phone is stored and if you take it out it isn't really the same phone any more.

The Three Types of SIM Card

There are currently three types of SIM card, but they all have the same chip; the only difference between the models is size. All three are small, and to make things more confusing, all have similar names.

Standard/Mini SIM

Standard SIM

  • The original SIM card
  • Introduced in 1991
  • Now very rare in new handsets
  • Measures 25 x 15mm

Micro SIM

Micro SIM

  • Smaller than the original SIM card
  • Introduced in 2010
  • Becoming less common in new handsets
  • Measures 15 x 12mm

Nano SIM

Nano SIM

  • The smallest model of SIM card
  • Introduced in 2012
  • In most new smartphones
  • Measures 12.8 x 8.8mm

How Do I Know Which SIM I Need?

If you are buying a handset with a phone contract, you should automatically be given the correct size of SIM card. If you are buying a handset or phone contract on its own, you should look at the product information for the phone and – failing that – call the retailer or manufacturer for advice.

What If I Have the Wrong SIM?

Having the wrong size of SIM is not a reason to worry. If your SIM card is a larger model than required for your new phone, you can contact your network provider for a new one. If your SIM is a smaller model, adaptors are cheap and readily available in stores and online.