Smart Phones

[EXPLAINED] Types of SIM Cards & Technical Specification

We use SIM cards in our mobile phones as our identity. It’s a removable module which has the capability to store information about the mobile phone and all the data that we require to make calls, messages and other things. However, there are many sizes and types of SIM cards that we will disclose later in this post.

What is SIM Card?

A small card/chip that we install inside our mobile phones to store subscriber(our) information. Every SIM card also carries a unique identification number(your mobile number) for its owner. The first three digits on this identity are known as the country code and they are different for every country. Then the second two digits are the identity of telecom company you’re using. The five digits may be same for many users but then the last 7 digits of your numbers are unique for every user.

How does SIM Card Work?

Equipped with an integrated circuit, SIM card stores the IMSI of the mobile subscriber. SIM Cards is the only way to authenticate the owner of the mobile phone on the communication system. Giescke and Deviant are the two mans behind SIMs who introduced the first-ever SIM card in 1991.

Every SIM card is fixed in a small smart card, so we can easily install and remove it from any mobile phone. This small-sized chip includes a unique ICCID, IMSI, SAI, PIN and a personal unblocking code. Also, the SIM cards use the network specific information verify the identity of users in the network.

What is GSM and CDMA Cards?

There are basically two types of SIM cards that we use, one is GSM and second is CDMA. They both are multiple access technologies.


One of the types of SIM cards which is using by more then 98% of mobile users right noe. GSM stands for Global systems for mobile that it was founded in 1970 by Bell Laboratories. It divides 200 KHz signals into eight 25 KMz times slots using the circuit switch technologies. The data transfer rate of GSM starts from 64 kbps and end with 128 kbps. Most of the telecom companies use GSM just because it carries all the information is a removable card.


Unlike the GSM, Code division multiple access(CDMA) is based on white lists to verify the specific subscriber. Currently, CDMA is functional only in the United States of America. It means that only limited mobile phones can use CDMA with the company’s permission. You can’t ever make a video call and transmit with 3G-CDMA networks. You can easily switch to GSM from CDMA but can’t switch to CDMA from GSM SIM. CDMA need a bit more processing power to operate as compared to GSM.

Difference Between Prepaid and PostPaid:

Now in GSM, there are also two types of SIM cards, Prepaid and PostPaid. It is always been complicated when we talk about Prepaid and Postpaid. The main difference between both packages is that in Prepaid you need to pay advance for everything and In Postpaid, you have to pay on monthly basis.

PrePaid SIM:

PrePaid is also known as prepayment, It’s a type of GSM, in which you need to pay for any service like messaging, calling and using the data connection. The mobile phone users who are limited consumers, prefer to choose PrePaid as their default connection. In Prepaid, you need to recharge or must have the balance on your phone before purchasing any package. Once the balance, the package is finished, you will not be able to use the service again until avail the package again.

PostPaid SIM:

Unlike the Prepaid, you need to pay on monthly basis in Postpaid SIMS. The user needs to pay after the services are received. Postpaid plans calculate everything that user spend everything and then send the bill just like your electricity bill. Postpaid is too costly as compared to Prepaid that’s the majority of cell phone users prefer to go with Prepaid.

Normally, In Postpaid you can choose a limited package for a month. The company will charge at a flat rate even if you use half of your selected package. But if you exceed your limited package, then you need to them extra.


1 Payment befor using service. Subsequent payment
2 Low in rates. Very High in rates.
3 Packages are rigid Packages are flexible.
4 Limited time credit. Unlimited credit.
5 No physical bill. Company will send a proper bill.

Keys of SIM Card:

  1. Every SIM card is integrated with a primary 19 digits number which is called ICCID. These 19 digits are consist of IIN, IAI and check digit.
  2. A SIM card has the capability to verify the subscriber of the network.
  3. Based on IMSI inside the SIM card, it authenticates the subscriber to check that if the legal user is online or not.
  4. It has about 128 kb storage allowing you to save you to save up to 1000 messages and 250 plus contacts.
  5. SIM card has all the applications(SIM Tool Kit or GSM 11.14) that provide basic information on demand.
  6. M-chatting, messaging and cell broadcast is on your phone just because of SIM card.
  7. It provides location based services. Also, have the feature of location area identity.

Types of SIM Cards:

There are three commonly used SIM cards out there. They are not different in functionality but in size. Looking at the SIM slot of your mobile phone, you need to get the correct size SIM.

1) Mini-SIM:

Mini simMini SIM is also known as standard SIM can be used in all the phones prior to 2012. Its size is 25×15 mm and largest in all the available SIMs till now. The sad fact about Mini SIMs is that the latest smartphones don’t support it. Nexus 5, all the Nokia’s simple phones and few more latest phones are still relying on Mini SIM.

2) Micro SIM:

Micro simA bit small in size as compared to Mini-SIM, It measures 25×12 mm. Micro SIM is now much popular as all the new coming Android devices support it. The main difference between Micro and Standard SIM is that Standard SIM is covered by plastic cover around the chip while Micro isn’t. Micro SIMs were introduced in 2010.

3) Nano SIM:

nano simYou do need a Nano SIM if you are using the iPhone. It is the smallest size available till now. Its size is about 12.3×8.8mm and it can be installed on Samsung new devices too like Samsung Galaxy S7 Edge.

Technical Specifications:

Well, Above we talk about the types of SIM cards, but these Mini, Micro and Nano SIM cards are only for mobile/smart phones. You may don’t know till now that SIM cards can be used other than mobile phone and communication purpose. If you are a credit/debit/master card holder then you can see a small SIM chip on it.

Specification of SIM card

Every SIM chip is consist of 6 different pins and every single pin has its own name and technical specifications.

PIN Name Specification/Functionality
1 VCC, VSIM The power supply of your SIM card
2 RST Reset (card initialization)
3 CLK Clock
4 GND Ground
5 VPP, SIMIN Programming voltage (for data entry on SIM)
6 DATA, IO Data flow IN / OUT

Dimensions of SIM cards:

There are actually 3 sizes/dimensions or types of SIM cards. The thickness of every SIM card is same and usually its about 0.8 mm.

SIM Dimension [mm] Note About the Dimensions
Full-size 85,6 × 54,0 Size as a normal plastic (payment) card
Mini-SIM 25,0 × 15,0 Standard SIM card for mobile phones
Micro-SIM 15,0 × 12,0  Small SIM card for more advanced and latest mobile devices
Nano-SIM 12,3 × 8,8 Cropped pins, for Apple phones and some latest mobile devices

Which one should I ask for?

There are two main things that you need to follow when buying a SIM card for your phone. One is the SIM card you’ll need and the second one is network performance of your SIM. Below are the few types of SIM cards with different performance speeds.

  1. To get the standard network performance, you need to buy the H1 SIM in any size.
  2. H2 SIM can help you get a strong network connection as compared to the H1.
  3. You need to buy the buy the H3 SIM card, if the H2 and H3 are not giving the result you’re looking for.
  4. H4 is the last and strongest standard of SIM card with the highest network performance rate.

I’m sure that you didn’t know these facts before, But Yes, it exists. The second thing you need to look into is the size of your SIM card. The depends totally on your mobile phone. There are many ways to find out which SIM gonna be fit on your phone and these ways are listed below.

  1. Switch off your mobile phone, take out the battery(If the SIM card-holder is under the battery) and measure it.
  2. If you have the box of your phone, then take the manual book out of it, open it and check which size you’ll need.
  3. Go to any company website and check it on the specifications page of you phone.

Luckily, all the telecom companies are now making 3-in-1 SIM cards. Both Nano and Micro SIMs are contained within Mini SIM. So you can easily pull out any SIM you need.

Also Read: How to Check Your SIM Card Number in Pakistan.

About the author


Pedro is an active blogger, web developer and UI Expert. I spent almost 10 years to get experties over various fields like Programing, SEO. Self motivated and with ownership I like to make things as close to perfect as possible. Also worked on, and enjoyed learning spectrum over the internet.

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