Have you ever noticed when using your new memory card that you don’t actually get the actual GB that’s written on the box? I took a deeper look into this and found the difference is between how brands label their memory cards and how your devices read them.
It’s a matter of definition.
What does 1GB mean to you? 1000MB is one GB, 1 MB is 1000KB and 1000 Bytes is 1KB. That makes sense to most people as it is the base 10 decimal system we are all familiar with. However, your computer actually calculates things differently.
What brands do: As we mentioned above, marketing and most people define a GB as 1,000,000,000 bytes, this is something that is easy to understand and easy to market.
What devices do: Computers operate on a base 2 binary system and define 1 GB as 1,073,741,824 bytes, and one KB is 1024 bytes. This is the value you see when you view the actual capacity in your card and technically it is called a Gibibyte, not Gigabyte.
Gibibyte?
Gibibyte or GiB for short is the base 2 binary system digital devices use. However “JEDEC” an international standards authority says it is ok to classify it also as GB. Because of this, there is a difference between what we think we are getting and what we actually see.
500GB = 464 GiB
When we buy a 500GB drive, what we really get is 500,000,000,000 bytes, in order to see what the computer will see we need to convert it.
Convert the base 10 GB it to base 2 binary GB (GiB):
In base 2 binary 1GB = 1,073,741,824.
500,000,000,000/1,073,741,824 = 465.66GiB.
On the computer: We see 465GiB of space, but it is shown as 465GB.
It’s all right in front of you!
Almost, if you look at the packaging carefully most boxes will show the GB definition.
Why not just make it the same?
Marketing and math’s use the decimal system where a gigabyte is easily divided into smaller units. As brands state their calculation on the packaging they are covering their back and stating exactly what they are advertising. In a base 10 world, you are getting what you paid for and this makes it correct, it’s a similar situation to our powerbank capacity investigation, where conversion occurs.
It doesn’t end there
Every card reserves some space for the file system and partitioning system so there is always a part of available memory taken or not shown. This depends on the format of the card as NTFS, FAT32, and ext4 have different size requirements.
Now you know the reason why the exact storage you see on the box will never match what you see when you plug it in. Remember, we live in a decimal world but compute in a binary system, so always remember the Gibibyte.
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