Currently, there are 3 SIM card sizes available on the market - standard, micro and nano. Just to add to the confusion, the standard SIM card size is sometimes referred to as a "mini" SIM. All iPhone 5 and iPhone 6,7,8 and the X models take the nano SIM card and many of the older Samsung phones, such as the 4,5 and 6 use a micro SIM card but the newer ones such as the Samsung s8 and the s9 use a nano SIM. For many other popular iPhone, Samsung and Nokia models, please see below.
We are often asked why there are different sizes as the sizes are quite nominal. While the official word is not out, it seems unlikely that the reason is to save space for more memory or other internal features in a phone (although oftentimes, that is the "official" reason manufacturers state). Rumor has it that by having three different sizes of SIM cards, this increases the chances that you will not find or figure out what SIM card size you need for your phone or you will get the wrong size and hence, will end up having to roam with your provider. Good for them, bad for you. In fact, about 5% of Cellular Abroad customers wind up placing a secondary order after realizing that they ordered the incorrect one initially. Hopefully, this information will help prevent you being one of the 5%. If your SIM card size is not in the chart below, please ask your carrier or simply use Google to find out what SIM card size your phone requires.
Please note that standard and mini are one in the same.