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Last updated: 12 January 2022
Every phone requires a SIM card in order to function properly. You will need a SIM card in your device in order to make calls or send messages. You will also need a SIM card in order to utilise your mobile data plan to access the internet.
However, SIM cards come in a variety of sizes, and it’s important that you get the correct size of SIM card for your particular device. This guide will explain the different sizes of SIM card, and help you to make sure you get hold of the right one for your phone.
What is a SIM card?
A SIM card is a small plastic card which has a microchip that contains the information that allows you to connect to your mobile network to send and receive calls, texts, and data. ‘SIM’ stands for ‘Subscriber Identification Module’ and verifies the unique identity of your device so that the information being sent over the airwaves can only be seen by your device.
SIM card sizes
There are three main types of SIM card that are still in use at present. There’s the Standard SIM, Micro SIM, and Nano SIM. The size of SIM card you need will depend on the phone that you have. However, there are ways to make smaller SIM cards work in devices which require larger SIM cards, and vice versa.
The largest of the three types of modern SIM card, the Standard SIM was mainly used in devices that were made before 2010. The Standard SIM measures 25x15mm.
These days it’s pretty rare to find a handset that requires a Standard sized SIM card, but it can still be found on some budget, basic-feature phones.
The only noticeable difference between the Micro SIM and its predecessor (the Standard SIM) is the amount of plastic that surrounds the metal microchip. The Micro SIM was developed as smartphones became smaller and the Standard SIM was too large to fit inside these newer, sleeker devices.
The Micro SIM came into use around 2010 and measures 15x12mm. It can still be found on some newer devices.
Most new smartphone devices these days use a Nano SIM card. Introduced in 2012, the Nano Sim measures 12.3x8.8mm. The Nano SIM almost entirely consists of the metal microchip with very little plastic surrounding it.
The Combi SIM is a Standard sized SIM card which has a Micro SIM contained within it. The card as it is will fit inside a Standard-sized slot, but if you need the card to fit a Micro-SIM device you can remove the additional plastic surrounding the card and it’ll fit inside a smaller slot.
Many cards supplied by mobile networks these days are 3-in-1 cards which contain a Nano SIM, inside a Micro SIM, inside a Standard SIM.
These kinds of cards allow mobile networks to supply a single card to their customers which they can modify to fit their device by themselves.
What size SIM card do I need?
You need to make sure that you order the correct size card for the device that you have. Most of the time the instructions which came with your phone will tell you which size of SIM card is required for your device.
If you don’t have this handy, you can do a Google search for your mobile phone model and you’ll be able to find what size of SIM card your device uses.
As mentioned earlier, many network operators supply 3-in-1 cards these days. If you aren’t entirely sure of which size card you need, you should be able to play around with the 3-in-1 card until you find the size that fits the SIM slot on our handset.
How do I identify which size of SIM I already have?
If you already have a SIM card and want to figure out which of the three sizes it is, you have a couple ways you could identify it. The quickest way is to search online for what the different cards look like and see how your card compares.
This can be tricky though, as Micro and Nano SIMs look quite similar without any reference point. This is when you may need to use a ruler. Micro SIMs are 15x12mm. Nano SIMs are 12.3x8.8mm.
Can I change the size of my SIM card?
It’s rare that you’ll have to modify the size of your SIM card, but there are ways that it can be altered if you ever find yourself in a position in which it has to be done.
One way you can make a smaller card fit inside a larger slot is by using a SIM adapter. Adapters are usually very cheap (around £1) and will allow you to convert any kind of smaller sized SIM card fit into any of the larger sizes of slot.
If your card is too large to fit in your device, you can cut it down to size. There are specialist tools that can achieve this, but you can also cut it with scissors if you’re in a pinch. There are tutorials online on how to do this, but be warned, if you damage your card there’s no way of getting it to work again.
Best SIM-only deals
There are plenty of SIM-only plans available on the market right now, but how do you find the right one for you without wasting an entire day? It’s simple. Just use our mobile comparison tool to compare the different deals on offer so you can find the cheapest one that suits your individual needs.