All smartphones (and feature phones and other types of mobile phones) require a SIM card to connect to a mobile network as, in fact, do mobile broadband devices, and any tablets that offer mobile connectivity.
But while youre sure to have at least one gadget in your life that needs a SIM card, not all SIM cards are the same, as they come in three different sizes and four different common types.
Below then well explain what those three different sizes are, which youre most likely to need, how to adapt a SIM card to a different size, whether you need a new SIM card for 5G, what an eSIM is, and generally tell you everything else you need to know about SIM cards.
There are different-sized SIM cards because it has become increasingly desirable to have smaller SIM cards, since that frees up more space in a (or other device) for other tech, without making the larger.
However, while that means that the most common SIM cards are a lot smaller than a standard SIM card, the older, larger SIM card sizes are still in use too in some older devices, and in some devices that dont need to make the most of their space.
There are five common SIM card types, which are as follows:
Nano SIM
A nano SIM is the smallest removable SIM card size, and its also the most modern (other than eSIMs, which well get to further down) having been introduced in . This is basically just a small integrated circuit with almost nothing around it, and its the kind used by the vast majority of modern devices.
Micro SIM
A micro SIM card is the middle size. These have more plastic around them than a nano SIM, but less than a standard SIM. They also have a slightly larger chip. In terms of smartphones, you might need one of these if your is over eight years old, but theyre rarely used in recent years. Indeed, they were introduced in , so theyre getting on a bit now.
Standard SIM
A standard SIM is the biggest SIM card size currently in use, and despite being thought of as the standard its the most rarely used. It has a large amount of plastic around the chip, and tends to only be found in the oldest of phones (and some other devices).
It was introduced back in , and as the oldest of them it was the standard for a while hence the name.
Note that standard SIM cards are also sometimes known as regular SIMs or mini SIMs the latter because there was an even bigger credit card-sized SIM card available when these launched, but theyre no longer used.
Combi SIM
A combi SIM (sometimes called a multi SIM or trio SIM) combines all three sizes of SIM card into one, so you can easily just pop out the one you need.
This is the type youll typically be sent by a mobile network, so you dont need to worry about requesting the right SIM card size. Note however that while youll be able to pop out whichever size you want, you wont then be able to make the SIM card bigger again, so if you ever need to move up a size, youll either need an adapter (explained below) or to request a new SIM card.
eSIM
An eSIM is an embedded SIM card (thats what the e is for) meaning that you cant remove it from your or other device. This is the newest type of SIM and its found in quite a lot of modern handsets, such as the iPhone 16 range along with many other iPhones and the Samsung Galaxy S24 range, among many other Samsung phones.
These are actually even smaller than nano SIMs, therefore freeing up more space for other tech. That small size means eSIMs are also used in wearables such as Apple Watches and Samsung Galaxy Watches.
But the main advantages of eSIMs include making it theoretically much easier to change networks and plans since you cant change the eSIM in your device, it needs to be possible to change network while keeping the same card, so theres no need to swap to a new one.
Plus, multiple networks and numbers can potentially be stored on an eSIM, so you can theoretically have multiple numbers on a single SIM. And you wont need to worry about navigating all the different SIM card sizes detailed above.
While many phones use these, at the time of writing its always in addition to a removable SIM card slot (at least for phones sold in the UK), so you never have to use an eSIM on a smartphone. Not all networks currently support them either, but its expected that these will become the standard SIM type eventually.
The chart below provides a clearer look at the exact size of each SIM card type. Youll note that combi SIMs arent included and thats because at their full size theyre the same size as a standard SIM, then if you pop out a smaller section it will match the relevant SIM card size below.
SIM Type
Height (mm)
Width (mm)
Thickness (mm)
Standard SIM25..000.76Micro SIM15..000.76Nano SIM12.308.800.67eSIM6.005.000.67SIM Card Sizes ComparedComparison of SIM card dimensions. Please note: nano SIMs and eSIMs are 0.09mm thinner than Standard SIMs and Micro SIMs.
No other differences exist between these SIM card types, its literally just the size. If there were other differences, then combi SIMs wouldnt really be possible. An eSIM meanwhile is quite different, as detailed above.
Which SIM card you have will depend on a number of things. If you received one recently its likely a combi SIM, since thats what networks tend to supply.
Failing that, unless its one that youve had for many years its probably a nano SIM, since theyve been the most common for 8+ years.
However, to tell for sure just look at the picture near the top of this article and compare the SIM card types to yours remembering that a mini SIM is another name for a standard SIM, and that an eSIM is embedded into the .
As for which you need, that will depend on your device, but the same general logic applies for most modern smartphones, youll want a nano SIM. However, since networks supply combi SIMs you shouldnt need to specify just order one of those and then when it arrives you can pop out the right size for your .
The exception is if you want to use an eSIM, in which case you will usually need to request one though many networks dont support them.
If you have the wrong SIM card size for your , then wherever possible the best thing to do is simply to request a new one from your network and get your number transferred to that.
However, there are alternative options. If your SIM card is too large for your , then you can buy a SIM card cutting tool. These tend to look a bit like a stapler, but they trim your card down to the correct size and shape.
If on the other hand your SIM card is too small for your , then you can get a SIM adapter. This is a plastic frame that you can put your SIM card in, to essentially upsize it to micro or standard size.
Both of these tools can be purchased, and some independent accessory stores and the like also offer SIM card cutting services. However, theres always a risk of damaging the card when cutting it, so we dont recommend it.
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Of course, none of these solutions apply to eSIMs either an eSIM only comes in one size, but if you want to switch to or from an eSIM then youll have to contact your network.
In most cases you wont need a new SIM card to access 5G if you have a 5G plan and a 5G , then your current SIM card should connect to 5G networks just fine. Your network may send a software update to your SIM card when it detects that youre trying to connect to 5G, but thats all.
Having said that, O2 claims at the time of writing that you will need a new 5G SIM card on its network. This wont be true in all cases as it now typically provides 5G SIM cards, but if for example you bought a 5G from the network before October 17th , then youll need to switch to a new 5G card.
O2 seems to be an outlier though, as Three, EE and Vodafone all claim that your current SIM card will work for 5G. MVNOs such as Tesco Mobile also claim that you wont need to switch SIM card, though some others dont specify one way or the other at the time of writing. So if in doubt, check with your network.
While were on the subject, its worth noting that youll still be able to connect to 4G and 3G networks with a 5G SIM card/plan, so you wont lose access to the older technologies by upgrading to the newer ones.
The different removable SIM card sizes include nano SIM (which is the smallest), micro SIM (which is the middle size), and a standard SIM or regular SIM (sometimes called a mini SIM), which is the largest. There are also eSIMs, which are even smaller than nano SIMs, but theyre built into the , so you wont see them.
Mobile networks supply something called a combi SIM, trio SIM or multi SIM, which includes all three possible removable SIM card sizes. This is usually offered as standard.
No, you need the right size SIM card, which in most cases will be a nano SIM. If your device is locked to a specific network, then you also need the SIM card to be for that network or to unlock your device.
All mobile phones use SIM cards but they dont all use the same size ones, so youll need one thats the right size for your . In most cases this will be a nano SIM.
Most smartphones made from around onwards will use a nano SIM card. That includes big name handsets like the iPhone 16 range, iPhone 15 range, iPhone SE (), Samsung Galaxy S24 range, Samsung Galaxy S23 range, and many, many more.
Nano SIM cards are the most common size most smartphones made from around onwards use a nano SIM card.
Yes, you can use a SIM card cutting tool to convert a standard SIM to a nano SIM. However, this isnt recommended as it risks damaging the SIM card. In general youre better off requesting a new SIM card from your network.
A mini SIM card is another name for a standard SIM. It was originally called a mini SIM because when it first launched there was a larger full-size SIM card in use too, but these larger ones are no longer used, so mini SIMs have become standard SIMs.
A SIM card adapter is a piece of plastic that you can place a micro or nano SIM card into to convert it into a larger size.
If you put your SIM card in another then as long as the card and support the same network people will then be able to call and text you on that , and youll be able to make calls and send texts of your own from it, using the same network and allowances as you had on your old .
numbers and other data may also be transferred along with the SIM card, if they were saved to the card.
A combi SIM is a SIM card that contains all three possible removable card sizes, with perforations allowing you to pop out the size you need. These are sometimes called trio SIMs or multi SIMs.
SIM cards all contain the same tech; however they vary in size, and are typically locked to a specific network.
In most cases you wont need a new SIM card your old one should work fine. However, on some networks (such as O2) a switch may be required. If in doubt, check with your network.
Yes. A 5G SIM card can still connect to 4G, 3G, and 2G networks. In fact, most 4G SIM cards already support 5G, so a 5G SIM card isnt really a different thing.
Update Published November 15,
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What is Nano SIM? How is it different from Micro SIM or SIM? Which iPad models use a Nano SIM card? How do you cut down a Mini or Micro SIM card to the size of a Nano SIM?
Nano SIM refers to the SIM (Subscriber Identity Module) standard used by the cellular capable iPad models.
Full-size "regular" iPad models with Nano SIM cards include:
Select iPad mini, iPad Air, and iPad Pro models also have Nano SIM cards.
All iPhone 5 and later iPhone models use Nano SIMs, too. Recent China/Hong Kong-specific iPhone models even support two physical hardware Nano SIMs.
These China/Hong Kong-specific dual Nano SIM models are:
Nano SIM is the fourth version, or the "fourth form factor" (4FF) of the SIM standard and measures a mere 12.3 mm by 8.8 mm by 0.67 mm, but still holds the same amount of data as earlier SIM cards.
Nano SIM is both smaller and approximately 15% thinner than the earlier Micro SIM (3FF) standard as well as the Mini SIM (2FF) cards that were ubiquitous for many years and people commonly refer to simply as SIM cards. Technically, the original SIM (1FF) card standard is the same size as a credit card and most people probably have never seen one in person.
This diagram compares the relative size of each SIM standard:
Photo Credit: Wikipedia (Justin Ormont)
As you can see, the Nano SIM (4FF) reduces the size of the SIM effectively to the gold contact area and has just barely enough extra insulating "card" around it to prevent electrical shorts.
Trimming a Mini or Micro SIM to Nano SIM
These days, it is not difficult to obtain a Nano SIM card -- or a 3-in-1 SIM card that can be used as a Nano SIM -- directly from a carrier. However, if it is more convenient for whatever reason, a Mini or Micro SIM also can be cut down to the Nano SIM size for use in the applicable iPad and iPhone models.
It is quite possible to cut a Mini SIM or Micro SIM down to the Nano SIM size with a sharp pair of scissors or a razor blade and there are templates designed for individuals interested in doing so. However, given the particularly tight tolerances around the contact area on the Nano SIM, it is not surprising that the Internet is littered with comments from people who ruined their SIM card in the process of attempting to cut it down by hand.
In theory, the cut SIM also should be "sanded down" to reduce its thickness, but many Mini or Micro SIM cards are thin enough already to fit in the standard Nano SIM carrier without the need to do so.
Rather than take a great deal of time and risk destroying your existing SIM card by cutting it down by hand, EveryiPad.com strongly recommends purchasing a proper Nano SIM cutter.
A Nano SIM cutter makes it easy -- line up the card correctly and press the handle. It's effectively the same process as using a handheld embosser and even if you consider your time to be unimportant, it costs about the same amount as messing up a single SIM card trying to cut it by hand.
The company is the world’s best What's a Nano Sim Card supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.