Nano SIM card and SIM card sizes: which one does your phone need?

Key takeaways

• A nano SIM card is the smallest removable SIM card, measuring 12.3 × 8.8 mm, and it's the size almost every smartphone sold in the UK.
• Physical SIM cards come in three sizes: standard (25 × 15 mm), micro (15 × 12 mm) and nano (12.3 × 8.8 mm). The chip inside is identical across all three, so only the surrounding plastic changes.
• The right SIM size depends on the phone, not the network or plan. If a SIM is the wrong size, an adapter or a replacement in the right size solves it, and cutting a SIM down risks damaging the chip.

 

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Nobody enjoys finding out a SIM doesn't fit while holding a tiny ejector tool and an already-opened pack.

The good news is that there are only three physical sizes, and the right one depends on your phone. Here's how to tell them apart, which one you probably need, and what to do if you've got the wrong one.

What is a nano SIM card?

A nano SIM card is the smallest removable SIM card. It measures 12.3 × 8.8 mm, about the size of a small fingernail, and was introduced in 2012.

It's also the size used by nearly every phone sold in the UK today. The iPhone 5 was among the first to use one, and Samsung moved to nano SIMs with the Galaxy S6 in 2015.

The chip inside is no smaller than on older SIMs. A nano SIM is the same chip with almost all of the plastic trimmed away, freeing up room inside the phone for other parts.

New to SIMs in general? Our guide to what a SIM card is starts from the basics.

SIM card sizes compared

Standard, micro and nano SIM cards all hold the same chip. Only the amount of plastic around it differs.

SIM size	Dimensions	Introduced	Typically found in
Standard (also called mini)	25 × 15 mm	1996	Older phones, mostly from before about 2012, such as the iPhone 3GS
Micro	15 × 12 mm	2003	Phones from roughly 2010 to 2014, such as the iPhone 4 and Samsung Galaxy S5
Nano	12.3 × 8.8 mm	2012	Nearly all phones today, from the iPhone 5 and Samsung Galaxy S6 onwards

Standard SIM

The standard SIM, sometimes called a mini SIM, is the old-school size at 25 × 15 mm. Before it came the full-size SIM, which was as big as a credit card.

Micro SIM

The micro SIM measures 15 × 12 mm and was the standard size for phones from roughly 2010 to 2014. It sits between standard and nano, with the same chip and slightly less plastic.

Which SIM size does your phone need?

Your phone determines the size, not your network or plan. Three quick checks will tell you:

1. Check the specifications. The manufacturer's website or the phone's manual lists the SIM type, usually as nano, micro or standard.
2. Go by age. A phone from about 2015 onwards almost certainly uses a nano SIM. This is a rule of thumb, so confirm with the specifications if you can.
3. Measure the SIM already in it. The long edge of a nano SIM is just over 12 mm, a micro SIM is 15 mm and a standard SIM is 25 mm.

Still not sure? A multi-size SIM has all three sizes in one card, so you can pop out the one that fits.

What if you have the wrong SIM size?

Don't panic. It's usually a quick fix:

• Ask your network for the right size. They can send you a replacement, and many will send a multi-size SIM that fits any slot.
• SIM too small for the slot? A snug plastic adapter lets it sit in the larger slot. Don't force it, as a loose one can jam.
• SIM too big for the slot? Skip the cutting tools. One slip can damage the chip, so a replacement is the safer option.

What about eSIMs?

An eSIM is a SIM built into the phone, so there's no card to match the size. It's set up digitally instead.

Not every phone supports eSIM, and many that do still have a physical SIM slot as well, so size can still matter. If you're curious how it works in practice, our “What Is eSIM guide” walks you through it.

Thinking about switching?

With SMARTY, you can order a free SIM or browse the plans first. They run month-to-month with no long contract, so there's no pressure either way.

Not sure what SIM-only means? Our guide to SIM-only deals explains it. Whatever size you're holding, it's nearly always a quick fix!

FAQs

1. Are all SIM cards the same size?

No. Physical SIM cards come in three sizes: standard (25 × 15 mm), micro (15 × 12 mm) and nano (12.3 × 8.8 mm). The chip inside is the same across all three, so only the plastic around it changes.

2. Can you use a nano SIM in a micro or standard SIM slot?

Yes, with an adapter, which is a plastic frame that lets a nano SIM fit into a larger slot. A snug adapter works well, while a loose one can jam in the slot.

3. How do I know which SIM size my phone needs?

The phone's specifications, whether on the manufacturer's website or in the manual, list the SIM type. As a rule of thumb, phones from about 2015 onwards use a nano SIM.