SIM Card Size Table
| Format | Introduced | Size (L × W) | Thickness | Note |
|---|---|---|---|---|
| Full-size (1FF) | 1991 | 85.6 × 54.0 mm | 0.76 mm | Credit-card ISO ID-1 |
| Mini-SIM (2FF) | 1996 | 25 × 15 mm | 0.76 mm | Cut down from 1FF |
| Micro-SIM (3FF) | 2003 | 15 × 12 mm | 0.76 mm | Cut down from 2FF |
| Nano-SIM (4FF) | 2012 | 12.3 × 8.8 mm | 0.67 mm | New chip, edge contacts |
| eSIM (MFF2) | 2016 | 6 × 5 mm | soldered | Chip on the motherboard |
The five SIM formats are one card at five stages of haircut. Full-size 1FF is a credit card (85.6 by 53.98 mm - it literally is the ISO ID-1 card); mini-SIM cut that down to 25 by 15 mm in 1996; micro-SIM to 15 by 12 mm in 2003; nano-SIM to 12.3 by 8.8 mm in 2012. The clever part of the ladder is what did not move: through the micro generation, the gold chip and its contact layout sit in exactly the same spot on every card, which is why the printed cut-down lines on old SIMs were real - a mini could genuinely become a micro, and a micro a nano, because the plastic around the chip was disposable.
Nano-SIM broke the pattern in two ways worth knowing. It shrank the chip itself and moved the contacts to the edge, so a nano cannot be cut from a micro - the industry stopped printing cut-down lines because the trick no longer works. And it dropped the thickness from the constant 0.76 mm to 0.67 mm, which is why the ladder only runs one way: a nano in an adapter sits noticeably proud in a micro slot, and a thicker-than-spec sandwich is the classic stuck-SIM recipe. The fifth row of the table is not a card at all: eSIM (MFF2) is a 6 by 5 mm chip soldered to the phone motherboard in 2016 onward - nothing to insert, nothing to lose, and the reason flagships ship with no tray at all in some markets.
How to use
- Identify a loose card by length first: 25 mm is mini, 15 mm is micro, 12.3 mm is nano - the widths differ too but the length separation is cleanest by eye and caliper.
- Run the ladder up, never down: any format fits a bigger slot through an adapter (nano into micro or mini frames), because the chip works electrically in all of them - but a card too big for the slot must never be trimmed at home once nanos are involved.
- Check thickness before forcing an adapter fit: 1FF through micro are all 0.76 mm, nano is 0.67 mm - if a nano-plus-adapter sits proud of the tray, use a proper nano adapter with the recess, or skip the adapter.
Frequently asked questions
Can I put a nano SIM in a micro SIM phone?
Yes - through an adapter, and it works electrically without compromise: the nano carries the same chip and credentials as any other format, and the adapter is just a plastic frame restoring the micro outline (and ideally the 0.76 mm thickness). The two cautions live in the mechanical layer. First, adapter quality matters: a sloppy frame can jam in the tray or misalign the chip, and a jammed adapter-SIM inside a phone is a repair-shop job. Second, thickness: nano is 0.67 mm against the family-standard 0.76 mm, so a flat adapter leaves the assembly under-thickness (usually fine) while the reverse trick - cutting a larger card down to nano - is exactly what stopped working when nanos moved the chip and contacts to the card edge. Going down the ladder with an adapter is safe; going up requires cutting that modern cards no longer support.
What is the difference between micro, nano and eSIM?
Three generations of the same idea at three levels of invisibility. Micro-SIM (15 by 12 mm, 2003) kept the full-size chip and contacts, just on less plastic; nano-SIM (12.3 by 8.8 mm, 2012) shrank the chip package itself, pushed the contacts to the card edge, and thinned to 0.67 mm - which is why the cut-down trick died with it; eSIM (2016) is not removable at all: a 6 by 5 mm MFF2 chip soldered to the motherboard during assembly, reprogrammed over the air by scanning a carrier QR code. Functionally all three hold the same subscription identity; the differences are mechanical and operational. A physical card moves between devices in seconds and dies with the tray; an eSIM cannot be lost, bent or stolen from a phone, but switching devices means re-provisioning through the carrier instead of swapping plastic.
Why was the thickness of nano SIM reduced?
Space accounting at the 0.1 mm scale. Phones in 2012 were racing to slimmer bodies, and inside them every tray, flex cable and battery layer fought for tenths of a millimeter; the SIM standards body (ETSI) shaved nano to 0.67 mm, finding a tenth of a millimeter between the tray floor and the battery without giving up the chip. Three generations of 0.76 mm constancy (full-size, mini and micro all share it) made the change visible: a nano alone sits shallow in a micro tray, and adapters must add back the missing tenth to keep the pin contacts pressing properly. The same logic explains why the thickness ladder runs one direction - a thicker-than-spec assembly (nano in a flat adapter, or worse, a taped-together sandwich) is the standard recipe for a SIM stuck in a slot, because the eject mechanism assumes the spec thickness to push the card to the release point.
Do I still need the full-size SIM card format?
Almost never as a card, but the format refuses to die on paper: 1FF is the ISO ID-1 credit-card outline, and some industrial, payment and legacy IoT terminals still ship with full-size slots because the big card doubles as a durable carrier (print it, punch it, laminate it). Consumer phones abandoned it with mini-SIM in 1996 and never looked back, and every modern slot takes nano or eSIM. The one place a full-size shell still helps a phone user is history: old SIMs were issued on ID-1 punches - pop the mini out of the credit-card frame and you understand the whole family, one chip at five sizes of plastic. If you meet a genuine full-size slot today, it is a device from the transition era or an industrial modem; the card it wants is your old SIM still living in its 1FF frame, not a new purchase.