Micro SIM card Size in mm & Inches

A micro SIM measures 15 x 12 mm and 0.76 mm thick. It is the 3FF (third form factor) SIM, introduced in 2003 but only widely used from about 2010, when the original iPhone 4 and a wave of Android phones adopted it. It sits between the older standard SIM and the newer nano SIM.

This guide covers the exact micro SIM dimensions, how it compares to the sizes on either side of it, and why so many people ended up cutting a standard SIM down to fit.

Quick Answer: How Big Is a Micro SIM?

A micro SIM is 15 mm long, 12 mm wide, and 0.76 mm thick, weighing about 0.5 grams. It is smaller than a standard SIM (25 x 15 mm) and larger than a nano SIM (12.3 x 8.8 mm).

Micro SIM Dimensions at a Glance

• Length: 15 mm / 1.5 cm / 0.591 in
• Width: 12 mm / 1.2 cm / 0.472 in
• Thickness: 0.76 mm, the same as a standard SIM and a credit card
• Weight: about 0.5 g
• Standard: ETSI TS 102 221, 3FF
• Orientation: one corner is bevelled so it only goes in one way

What Does a Micro SIM Look Like in Size?

A micro SIM is roughly the size of an adult index fingernail, or a standard SIM with most of the plastic frame removed. Its contact pads are the same as every other SIM; the card is just trimmed close to them, leaving a narrow border.

6 Everyday Comparisons for a Micro SIM

1. A nano SIM (12.3 x 8.8 mm) is 2.7 mm shorter, 3.2 mm narrower, and a little thinner.
2. A standard SIM (25 x 15 mm) is 10 mm longer and 3 mm wider, with a much bigger plastic surround.
3. An adult index fingernail is a close visual match.
4. A microSD card (15 x 11 x 1 mm) has almost the same 15 mm length and is 1 mm narrower.
5. A pencil eraser (the metal-ferrule end, about 7 mm) is roughly half the micro SIM’s length.
6. A credit card (85.6 mm long) is a little under 6 micro SIMs end to end.

Micro SIM Size in Different Units

Why People Cut Standard SIMs Into Micro SIMs

When micro SIM phones arrived, many carriers were still issuing standard SIMs. Because every SIM has the same contact layout in the same place, a standard SIM can be trimmed to micro size with a template or a punch tool, and the phone reads it fine. The catch is thickness: both cards are 0.76 mm, so a clean cut works, unlike cutting down to nano size where the older card is too thick.

The micro SIM was a short-lived middle step. By 2013 most new phones had moved to nano, and today micro SIM slots are mostly found on phones from roughly 2010 to 2014 and some budget or industrial devices.

Common Mistakes When Comparing Micro SIM Size

1. Assuming micro and nano are interchangeable. A micro SIM will not fit a nano tray, and a nano SIM rattles loose in a micro slot without an adapter.
2. Thinking the size affects storage or speed. It does not. Form factor is purely mechanical.
3. Cutting on the wrong lines. The contact pads must stay intact and centred; a bad cut kills the card.
4. Forgetting the bevel. The clipped corner sets orientation; forcing the card in the wrong way can damage the tray.
5. Mixing up length and width. A micro SIM is 15 mm long and 12 mm wide.

Frequently Asked Questions

What size is a micro SIM?

15 x 12 mm, and 0.76 mm thick.

Is a micro SIM bigger than a nano SIM?

Yes, by about 2.7 mm in length and 3.2 mm in width, and it is slightly thicker.

Can I cut a standard SIM to micro size?

Yes. Both are 0.76 mm thick and share the contact layout, so a template cut usually works.

Can a micro SIM be used in a nano slot?

Not without cutting it down, and cutting micro to nano is risky because of thickness.

How much does a micro SIM weigh?

About 0.5 grams.

Which phones use a micro SIM?

Mostly devices from around 2010 to 2014, such as the iPhone 4 and 4S, plus some later budget and industrial phones.

What is 3FF?

“Third form factor,” the industry name for the micro SIM.

Final Takeaway

A micro SIM is 15 x 12 mm and 0.76 mm thick, weighing about 0.5 grams. It is the 3FF form factor, a step between the standard SIM and the nano SIM, and because it shares its thickness with the standard SIM, it was the one size people could reliably cut down at home.