How many different kinds of SIM are there?

Not all SIMs are created equal. In this article we will cover the range of SIM sizes that are available, also the two variants that you can get each SIM type in. The IoT device you plan to use is likely to drive the SIM size you need, unless of course the SIM is already in the device as an eSIM or iSIM.

SIMs come in five sizes:

Full-size SIM – also known as 1FF

Introduced in 1991, this is the original SIM card, literally a card as it was the size of a credit card, 85.6mm x 53.98mm x 0.76mm. These are obsolete now as they are no longer used by any devices, let alone IoT devices.

Mini SIM – also known as 2FF

A significant size reduction from the Standard SIM measuring 25mm x 15mm x 0.76mm. Arriving with 2G/GSM handsets it is the SIM most people will recognise and is still in use today. Some device manufacturers and service providers refer to this as the “standard SIM”, despite being technically a second-generation derivative of the first SIM card.

Micro SIM – also known as 3FF

A further size reduction taking the SIM down to 15mm x 12mm x 0.76mm. This was first used by various networks for the launch of the original iPad in April 2010, and iPhone 4 in June 2010.

Nano SIM – also known as 4FF

This took the size of the SIM down further still, reducing the size to 12.3mm x 8.8mm x 0.67mm. This was the forts time the thickness of the SIM card had been reduced and was an indicator that they were hitting the limits of reduction. iPhone 5, released in September 2012 was the first device to use a Nano SIM.

The limiting factor for SIM size reduction has always been the need to maintain backward compatibility. To simplify the management of SIM stock and reduce potential confusion it was agreed that the contact patch footprint – the areas where the SIM makes electrical contact with the device – had to be maintained. That has allowed the now familiar SIM card to be sent out containing 2FF to 4FF SIM sizes, ironically often the same size as the obsolete original 1FF card. The cut outs allow the user to press out the size of actual SIM that they need.

different sizes of SIM cards

Embedded SIM – also known as MFF2

As the name implies the Embedded SIM (or eSIM) moves the SIM from a separate item to becoming an intrinsic part of the device. As it is directly soldered onto the device circuit board it improves reliability and removes the size limitation imposed by the need to maintain the contact patch footprint. Still a separate element from the rest of the device electronics the integrity of the security earlier SIM form factors had is maintained. Typically, eSIMs measure 6mm x 5mm x 1mm and were first introduced in 2016.

embedded size

The SIM card has been through many changes, and in its latest incarnations included as a part of the device. The next generation takes the size reduction even further as with iSIM it is no longer a separate physical entity, it is simply a secure area in silicon already in the device.

For both eSIM/MFF2 and iSIM it is important to remember that as a user you will not be able to change network provider in the way you could previously. You will need to get the Bootstrap Provider for the specific SIM to make the change for you. You will usually be advised on that when you purchase the device. It is all done over the air, and so whilst it may seem like a further step, it can also be a real help for devices out on the field. You can find out more in our article here [SIM vs eSIM vs iSIM].

For 2FF, 3FF and 4FF SIMs there are two different types of physical SIM available. It is important to consider where your IoT device will be deployed, and what conditions you need it to cope with.

You can get:

Standard SIM - The ones usually supplied by service providers and the ones used in phones. For most IoT applications these are the right choice.


Industrial SIM - If the IoT device is going to be used in a harsh environment, extreme temperatures (from -40°c to +105°c), or risk of corrosion, such as in the engine bay of a vehicle, it would be wise to get an Industrial SIM. These are specifically designed to continue working on hostile environments as their contact patches are better protected in ruggedised casings.

Whilst it possibly seems the least important part of your IoT solution, understanding the different options, both in terms of size and capability is a necessary step. Making the right choices will give your IoT solution the best chance of success, and trouble free life.

Take a look at our SIM v eSIM v iSIM article to find out how the evolution of the SIM card makes economic sense for IoT applications.