Full size, micro or Nano SIM? It can be confusing working out which SIM your phone needs. Here is what you need to know.
Phone SIMs currently come in one of three sizes, but the reality is that all of these SIM sizes work off the same electrical circuitry. The larger sizes simply have more plastic around the main SIM circuit for ease of handling and durability.
Older phones use the full sized SIM card. Technically it should be called the Mini SIM, because the very first SIM card format was even larger, but it's informally called the Full Sized SIM by most providers. Newer phones will either use a Micro or increasingly, the smaller Nano SIM format. The vast majority of mid-range and premium phones now utilise Nano SIMs, but it's not uncommon to find Micro SIMs still in use on budget handsets, or if you purchase a model that's more than a couple of years old.
If you’re buying a phone on contract your provider will provide a suitable sized SIM card for you to use, but if you’re in the prepaid or month to month SIM-only market you’ll need to match your SIM card size to the phone of your choice.
Most providers will offer a multi-sized SIM package that starts out as a full-sized SIM with the ability to pop the Micro- or Nano- sized SIM from the larger SIM. It’s wise to know the size you need to pop out, however, as if you go too small it can be difficult to reinsert it into the plastic of the larger card, and that's likely to cause problems in any case.
Which SIM size do I need?
When in doubt, consult your phone’s manual, or its freely available online specifications. Nano SIMs are the norm for premium handsets such as the iPhone XS or Samsung Galaxy S10, and in some cases the size required may be printed on the SIM tray or area where you insert the SIM card into your phone. You can always check with the merchant you’re buying the phone from, as they should know.
Should I use a SIM card adaptor?
If you’re swapping between phones that use only Nano or Micro SIMs it’s no fuss at all, but you may find yourself having to switch back to a Micro SIM if your existing premium phone is lost, stolen or broken.
One approach often used to handle the size difference between a Nano and Micro SIM is to use a SIM card adaptor. These aren’t much more than the replacement plastic (or sometimes metal) that makes up the "missing" space on a Nano or Micro SIM so that you can use them in a phone that takes a larger sized SIM.
Most manufacturers don’t recommend the use of SIM card adaptors, however, and for good reason. Because the SIM sits in the adaptor, there’s a high probability of it moving when you insert or remove the sim, scraping plastic or metal across the delicate internal pins that connect to the SIM card itself for proper operation. These can very easily snap, at which point you’re looking at an expensive phone repair. Comparatively, picking up a new SIM card is a much cheaper prospect. You can check out our guide to porting your existing mobile number to a new SIM here.