SIM card sizes: what a nano SIM is and how it differs from micro SIM and eSIM

Phones today mostly use the nano SIM, which ETSI specifies at 12.3 mm wide and 8.8 mm high. Older and larger sizes are the micro SIM, which ETSI calls the Mini-UICC, and the plug-in UICC. An eSIM is a chip built into the phone, so it has no card size to insert.

How many SIM card sizes are there, and what are the dimensions?

ETSI TS 102 221 (V17.1.0) specifies four UICC form factors: the credit-card-sized ID-1 UICC, the Plug-in UICC, the Mini-UICC and the 4FF, which is the nano SIM. The table summarises the sizes in ETSI's wording.

How does a nano SIM differ from a micro SIM?

The main difference is size and thickness. A nano SIM is smaller and thinner than a micro SIM, and it holds the same kind of chip with the same job; the plastic border is simply cut down to fit the tray of newer phones.

• Match the size to your phone's tray; Apple, for example, lists the iPhone X, 8, 7, 6s, 6, 5s, 5c and 5, and the iPhone SE (2nd generation or earlier), as nano-SIM-only models.
• Use only the tray that came with the phone, as Apple instructs.
• Place the nano SIM with the gold contacts facing up, as Samsung advises, and insert the eject pin straight into the tray hole.

Is it safe to use an adapter or cut a SIM yourself?

Cutting a SIM yourself risks damaging the chip, and an adapter thicker than the standard can jam inside a phone tray. The safer route is to ask the provider for the size your phone takes, or to choose an eSIM if the phone supports it.

What is an eSIM, and how does it compare with a nano SIM?

GSMA SGP.22 defines a technical solution for the remote provisioning and management of the eUICC in consumer devices. The eUICC is the embedded chip, and operator profiles are downloaded onto it. ITU-T E.118 (09/2025) calls a SIM an eSIM when its eUICC holds multiple profiles that can be updated over the air.

An eSIM is installed with an Activation Code that the provider issues, which SGP.22 says can be typed in or scanned as a QR code. The full steps are covered elsewhere; see the guide “Seven mistakes first-time eSIM users make” for the common slips.

What are dual nano SIM, nano SIM plus eSIM and dual eSIM?

Dual nano SIM means two physical SIM slots. Nano SIM plus eSIM means one physical card and one eSIM profile. Dual eSIM means two eSIM profiles active together, where the phone and the carrier allow it.

Which phones are eSIM-only with no SIM tray?

Apple states that an iPhone without a SIM tray supports eSIM only. Models bought in the United States include the iPhone 14, 15 and 16 families (with the 16e), the iPhone 17 and later, and the iPhone Air. Google says a Pixel 10 or later bought in the US, except the Pixel 10 Pro Fold, can use only an eSIM.

• Phones bought outside the US usually keep both eSIM and nano SIM, but some of the newest models can differ.
• Apple says that in mainland China, Hong Kong and Macao only some models support eSIM.
• Check your model on Apple's Support page on which SIM type your iPhone uses.

How should you keep your Thai SIM and add a travel eSIM abroad?

A common approach for Thai travellers is to keep the Thai SIM for bank OTP messages and incoming calls and add a travel eSIM as the data line. Apple says an iPhone can use one cellular data network at a time, and Google says only one SIM on a Pixel can be the default for data.

• Before you fly, check that the phone is not carrier-locked; Apple says to look for No SIM Restrictions next to Carrier Lock in Settings > General > About.
• Install the travel eSIM on Wi-Fi before departure, then turn on Data Roaming for that line on arrival.
• If your phone is a dual nano SIM model only, ask whether it supports eSIM before you buy one.

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