Nano SIM card, micro, standard and eSIM: every size measured

Nano SIM card, micro, standard: the sizes compared

A nano SIM card measures 12.3 mm by 8.8 mm and is the size almost every phone with a tray takes today. It's the smallest of the four removable formats defined by ETSI, the European standards body that writes the SIM specification. The others are bigger plastic around the same chip.

The names are a trap. What shops call a "mini SIM" is ETSI's plug-in card, the standard size, and ETSI's "mini-UICC" is the micro. If someone offers you a mini SIM, they almost certainly mean the big one.

Dimensions come from ETSI's TS 102 221, version 18.3.0, which we read on 9 November 2026 along with Apple's, Google's and Samsung's support pages.

What is a nano SIM card?

The fourth form factor, or 4FF. ETSI approved it on 1 June 2012, describing it as 40% smaller than the smallest SIM then in use and offering "the same functionality as all current SIM cards". Less plastic, same chip, same job. It's also thinner than the older cards, at 0.67 mm.

Apple's list shows every iPhone with a tray, from the iPhone 5 on, takes a nano-SIM. Google says all Pixel phones can use nano SIM cards. Samsung's dual SIM page describes nano SIMs in its S21 tray, while noting that tray and SIM size vary by model and pointing you to the device's specifications. If you own a phone made in the last decade, nano is the answer nine times in ten.

Which SIM card size do I need?

The quickest check is the tray itself. Eject it and look at the cut-out. A nano slot is barely larger than a fingernail.

If you'd rather not, the maker will tell you. Apple keeps a page listing which iPhone and iPad models take which SIM. For Android, the specifications page for your exact model is the place to look, since Samsung alone sells single, dual and hybrid trays across its range.

Some phones take no card at all. Apple says iPhone 14 models and later bought in the United States can only be activated with eSIM, and Google says a US Pixel 10, 10 Pro or 10 Pro XL can't use a physical SIM. No size of SIM fits a phone with no slot, and no adapter helps.

Do SIM card adapters work?

A nano-to-micro or nano-to-standard adapter is a plastic frame with a nano-shaped hole. The SIM drops in, and the frame makes up the difference so a small card sits correctly in a bigger slot. The chip does the work; the plastic is packaging.

They do work, mostly. We'd still use them only as a stopgap. A loose frame can shift inside a tray, and a card that slides out of its adapter inside the phone is a far worse afternoon than visiting a shop. Apple doesn't mention adapters, but it is clear about the cruder fix: a SIM cut or modified to fit a different device "might prevent connection to cellular networks", and damage to the tray from one isn't covered by its warranty.

Going the other way, from big to small, isn't an adapter job at all. It means cutting, and the better route is asking your carrier for a new card in the right size. That has a second benefit. Google warns that some older SIM cards aren't supported on Pixel 8 and later phones, which show "This SIM is no longer supported" and send you back to the carrier anyway.

What is a USB SIM card adapter?

Something else entirely, despite the near-identical name. A USB SIM adapter, or reader, lets a computer read a SIM directly, which people mostly use for old contacts saved to the card. It doesn't put a phone line on the computer. Don't confuse it with a USB mobile modem, the dongle that takes a SIM and does connect a laptop to a network. For a trip, your phone's hotspot does that job without another gadget.

Where does eSIM fit?

It's the size that isn't one. An eSIM is a chip soldered inside the phone, which ETSI's specification already allows for as a "non-removable" module. You download a profile instead of pushing in a card, so the size question disappears. Apple calls it "an industry-standard digital SIM built into your iPhone". Our what is an eSIM explainer covers the rest, and eSIM compatible phones lists which handsets have one.

What size SIM should you buy abroad?

Nano, unless your phone tells you otherwise. In practice a local prepaid SIM rarely forces the choice. ETSI's 2012 release said the nano could be packaged to stay backwards compatible with older designs, and that's how carriers ship it: a full-size carrier card with the SIM in nested cut-outs, so you snap out the size your phone takes. Snap carefully. Once the nano is out, the micro frame around it is gone too.

Check two things before the size. First, that your phone is unlocked, or the card is useless whatever its shape. Second, whether your phone has a tray at all; if it's a US iPhone 14 or later, it doesn't. Our iPhone eSIM guide has the model list.

Then compare the plastic with the alternative. A local SIM at the airport costs about $7 in Vietnam, $12 in Japan and $20 in the USA, on the typical prices in our guides. We don't hold what data those cards include, so treat them as entry prices. Still, $7 in Vietnam is under a fifth of the $39 for the best-value eSIM there, Nomad's 50 GB. In the US, $20 is roughly what a 10 GB eSIM costs: Airalo's is $22.50 for 30 days. The cheapest eSIM table shows both numbers side by side for each country we cover.