Why MicroSD cards and internal storage do not contain as much capacity as advertised

Hello and welcome to another post. Let’s look at why microSD cards and internal storage do not contain as much capacity as advertised.

A microSD card is an external or secondary storage device that can be inserted into a smartphone. It’s primary purpose is storage of files.

An internal storage is an embedded storage module that acts as the primary unit of storage for a smartphone.

The amount of space that a storage device has is called it’s storage capacity. In many cases, a lot of these storage capacities are wrongly reported. The actual storage capacity is lesser than the advertised storage.

Why is that?

Why microSD cards and internal storage do not contain as much capacity as advertised

There are two main reasons why:

  1. GB vs GiB
  2. File system overhead

GB vs GiB

Now this first thing you need to know is that the way we calculate storage capacity and the way computers calculate capacity are very different.

To us regular people…

  • 1KB = 1000B
  • 1MB = 1000KB = 1000^2B
  • 1GB = 1000MB = 1000^3B
  • 1TB = 1000GB = 1000^4B

It makes sense because humans count and calculate in decimal (that is to the power of 10).

Computers on the other hand do not count or calculate to the power of 10. Instead they use binary (that is to the power of 2).

So using computer logic and binary

  • 1KiB = 1024B
  • 1MiB = 1024KB = 1024^2B
  • 1GiB = 1024MB = 1024^3B
  • 1TiB = 1024GB = 1024^4B

The ‘i’ is inserted to let the reader differentiate between the capacity calculated by computers (in binary) and the capacity calculated by humans (in decimal).

So 1MB =/= 1MiB

So now that we are armed with this knowledge, let’s put it into real life practice.

I have a class 10 32GB SDHC card. Since it’s size is 32GB in human language, what is the actual size in machine language?

Let’s turn to mathematics for this one.

To convert from GB to GiB

Divide (1000³ / 1024³), the answer is 0.931323.

Use the answer to multiply 32GB.

32 × 0.931323 = 29.8GiB

So you can clearly see that my 32GB memory has magically become 29.8GB.

Let’s move on to the second reason.

File systems

The file system as I have already extensively explained here is a system used to arrange files on a microSD card or computer storage.

The file system on my microSD card was definitely fat32 from the factory but I have formatted it using Android. This file system logic or code will also occupy a certain amount of space on the microSD card.

It is very small, yes but I can not boldly state the actual size. This will further reduce the space available on the microSD card.

So let’s crosscheck our science and maths with real life to see if it’s true…


My 32GB SDHC card is actually 29.52GB.


You can see that 29.52GB is not as sexy as 32GB for advertising. I don’t think I need to tell you the one that the company chose to advertise.

Let’s get to internal storage

I have said this here before and I’ll say it again. In 2012, 4GB was huge to me. Around 2014/15, I was very okay with 8GB of storage.

In 2017/18, I survived very well on a 32GB storage. In 2019, I did well on a 64GB storage.

Now? I cannot even imagine the thought of struggling with a 64GB storage. The only reason I’ll do so is if I have a 128GB card to act as secondary removable storage.

Once upon a time, 4, 8 and 16GB were the default storages. The bottom of the barrel. Now it’s 32GB and 32GB is fast going into oblivion for 64GB.

I know more than most people how hard money is but do not settle for anything less than 64GB. Optimally, it’s 128GB you should be aiming at.

This is because the space advertised is not the same as the space that is available. This is very clear.

So if you have a 32GB internal storage that’s actually like 29GB+…

The operating system is going to be stored on the 29GB. Let’s assume that Android 11 is 15GB for example. That’s only around 14GB left for you as the user to use.

On a 64GB storage however, you’ll have a bit more breathing room. On a 128GB storage, you can spread your wings and relax.

Thank you for reading to the end. As always, ensure to check out our links for more information