iPhone with a SIM card and SIM card holder next to it

What SIM card do I need for my phone?

As technology advances, mobile phones have started becoming smaller, thinner, and sleeker (with some even starting to fold too!). As phone sizes change, the hardware needs to adapt as well, which has led to SIM cards being created smaller and smaller to fit inside. At the moment, we have three different SIM card sizes in the UK. Check out which size is needed for your smartphone in this guide. 

What is a SIM card?

A SIM card is a “Subscriber Identity Module” which allows you to connect to a phone network so you can make and receive calls, text messages, and use mobile data.   

These little cards hold important information about your smartphone, such as its number and network provider. The unique identification number on every SIM card is used to associate your number, minutes, and other account details. 

Regardless of what phone you have, everyone needs a SIM card for it to function properly. 


What are the different SIM sizes?

At the moment in the UK, there are three common SIM card sizes: Standard, Micro and Nano


SIM card












Standard SIM card

The Standard SIM card is the biggest of the three, at 25mm x 15mm. It’s not as commonly used anymore, but is usually still the compatible choice for older phones or less high-tech models with bigger space inside for hardware. 

Micro SIM card

The Micro SIM is a size smaller than the standard SIM, measuring 15mm x 12mm. It was first introduced in 2003 and became more known in its usage after being implemented into the iPhone 4. However, like the standard SIM, it’s becoming increasingly obsolete, as modern phones nowadays favour the tiny Nano SIM card. 

Nano SIM card

The Nano SIM is the smallest (and most common) SIM card size at the moment, coming in at a tiny 12.3mm x 8.8mm. Launched in 2012, they’re also the newest SIM size available right now and are compatible with most recent smartphone releases. There’s hardly any plastic border around the chip, so it would be interesting to see how SIM cards could get any smaller than this. 

Not for a phone: eSIM

Though not used on smartphones as of yet, there is a fourth SIM type, eSIMs, that are compatible with smartwatches. Unlike the three above, it’s built into the device and can’t be removed. It allows the device to act like a stand in for a phone. 


Can you change your SIM card size?

Most modern SIM cards come with an adapter that allows you to pick whichever size you need - simply pop the SIM out and you're ready to go.

If you kept this adapter, you can easily change your SIM card. The chip part will neatly fit into the plastic frame to become either a nano, micro, or standard SIM. whichever If you've lost the adapter, you can easily buy one online.

Most modern SIM cards come with an adapter that allows you to pick whichever size you need - simply pop the SIM out and you're ready to go.

If you kept this adapter, you can easily change your SIM card. The chip part will neatly fit into the plastic frame to become either a nano, micro, or standard SIM. If you've lost the adapter, you can buy one online for a few pound.

Can you convert a standard SIM to a nano SIM?

This is slightly more tricky. If you’re using an old fixed size SIM card, you need to somehow make it smaller. 

You could very carefully cut it to size (avoiding the chip at all costs). In doing this though you’re risking damaging the SIM. 

The best thing to do is contact your network, who should be able to send you a replacement SIM. 


Which SIM card does my phone need?

If you’re switching networks or have just purchased a new phone, you’ll need to swap your SIM out for a new one, but you might not know what type of card size you need. As we’ve said, many older phones tend to use a Micro SIM, but the majority of newer releases are so small that only a Nano SIM would fit. Here’s a quick breakdown of what some manufacturers and their models require.


  • iPhone 12s: Nano SIM
  • iPhone 11: Nano SIM
  • iPhone Xs: Nano SIM
  • iPhone 8s: Nano SIM
  • iPhone 7s: Nano SIM
  • iPhone 6s: Nano SIM
  • iPhone SE (2016 & 2020): Nano SIM


  • Galaxy S6 to Galaxy S21 series: Nano SIM
  • Galaxy Note 7, 8, 9, and 10: Nano SIM
  • Galaxy S6, 7, 8, and 9 series: Nano SIM
  • Galaxy Note Edge: Micro SIM
  • Galaxy A series: Nano SIM
  • Galaxy J series (2016): Micro SIM
  • Galaxy J series (2018): Nano SIM


  • Honor P40 series: Nano SIM
  • Honor P30 series: Nano SIM
  • Honor P20 series: Nano SIM
  • Honor P10 series: Nano SIM
  • Honor P9 series: Nano SIM
  • Honor P8: Nano SIM
  • Honor P8 Lite: Micro SIM
  • Honor Mate 9 series: Nano SIM
  • Honor Y series (2017): Micro SIM


  • All Pixel phones: Nano SIM


  • Xiaomi Mi Note 10 series: Nano SIM
  • Xiaomi Mi 10 series: Nano SIM
  • Xiaomi Redmi 6, 7, 8, and 9 series: Nano SIM
  • Xiaomi MIX series: Nano SIM
  • Xiaomi Mi Note and Note Pro: Micro SIM or Standard SIM


  • LG G6, G7, and G8 series: Nano SIM
  • LG G5 series: Nano SIM
  • LG G2, G3, and G4 series: Micro SIM
  • LG V10 and V20: Nano SIM


  • Nokia 7 Plus: Nano SIM
  • Nokia 6: Nano SIM
  • Nokia 5.1: Nano SIM
  • Nokia 3.1: Nano SIM
  • Nokia Lumia series: majority require Micro SIM (exempt: Lumia 1520, Lumia 735, Lumia 830, Lumia 930)


  • Doro 8080: Nano SIM
  • Doro 8050: Nano SIM
  • Doro 7010: Micro SIM
  • Doro 6040: Micro SIM
  • Doro 5516: Micro SIM
  • Doro 1360: Micro SIM

If your phone model isn’t on here, don’t worry. A quick internet search or browse through your mobile’s instruction manual will tell you what SIM card size you need. 

If you order a SIM from us, we’ll send you all three sizes so you’re guaranteed to have the card you need. 


Where is the SIM card slot located?

If you’re changing SIM cards, you’ll have to remove your current one and place your new one inside. This means locating the SIM card slot and popping it open. Your card slot may be found in one of three places:

  1. Exterior on the side - sometimes you can only access your SIM card through the interior (see 2 and 3), but on many iPhones and Androids the slot is on the exterior. Turn your phone on its side and see if you can spot a little cover with a tiny pin-hole beside it. You can use the SIM ejector tool that will be supplied with your SIM cards to push the card tray open
  2. Under the back cover - if the back cover on your phone is removable, you may be able to find your SIM card slot underneath by simply lifting the back off
  3. Under the battery - if your battery is removable, the SIM card tray may be under this


How can I change my SIM card?

Once you’ve located the SIM card slot, all you need to do is open it and take the old SIM card out. This SIM is now effectively useless for you if you’ve swapped networks, so you can either keep it somewhere safe or destroy it (as it still stores your personal information).

When you insert the new SIM card, there’s a 45-degree notch in one corner that will align with the tray, so you’ll know which way to insert it. Once inserted, simply close the tray and place the cover back on your phone (if that’s how it was accessed).

If you need help changing your SIM, watch our video guide:


Asda mobile SIM only deals

Starting a SIM only journey with Asda mobile is quick and simple. All you need to do is browse our SIM only deals and pick a bundle that best suits you! 

If you’re moving to our network from a different provider, you’ll need a PAC code to keep your number.


Discover more about SIM only

If you’re not sure whether SIM only is right for you, check out our blogs on all the advantages and benefits you can reap from this type of phone plan:

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