These are all storage capacities and can refer to memory ( RAM) or hard drives and SSDs (solid-state storage). Things get complicated by the fact that some manufacturers play fast and loose with their conversions, so you might find your 500GB drive doesn’t actually have 512000MB of usable storage. Read on and you’ll find out why, as well as how to convert between MB, GB, TB and the difference between megabytes and megabits.
What’s a megabyte?
Computer storage is measured in gigabytes (GB) and terabytes (TB), among other units. Your phone will have a number of gigabytes in which to store apps, music, contacts, emails, messages, photos, videos and more. Don’t confuse storage with memory. Memory, or RAM, is there only to store files and data temporarily while they’re being used. That’s why the amount of memory is much smaller – a phone might have 128GB of storage but only 4GB of memory (RAM). The hard drive in your PC or laptop will probably have hundreds of gigabytes. External hard drives and network attached storage (NAS) might have a similar capacity or even thousands of gigabytes, which are called terabytes (TB). Here’s how it all works:
1TB = 1024GB1GB = 1024MB1MB = 1024KB1kB = 1024 Bytes1 Byte = 8 bits1 bit = 0 or 1
Note: this doesn’t cover SI units, which work on the basis that kilo means 1000.. This means there are two different approaches to quantifying storage, one which uses the power-of-two (shown above) and the other which uses the power-of-ten which makes 1KB = 1000 Bytes. That’s why you’ll see kilobytes referred to as kibibytes and Megabytes as mibibytes in order to differentiate them. However, most people still use Megabytes to mean 1024 kiloBytes even if they really should say MibiBytes, and the same with GB and TB. Computers work using the power of two, not the power of 10, because they’re binary machines, which is why the power-of-two should be applied to computers (and phones, tablets and any other electronic gadget). Here’s a more detailed explanation, with examples. Bit: Computers deal with binary digits, or bits for short. A bit can be 0 or 1, equivalent or off or on. Byte: One byte is eight binary digits, such as 1111001. Kilobyte (kB): The smallest file stored on a smartphone, tablet or PC is typically four kilobytes (4KB) in size. A kiloByte is 1024 Bytes. Therefore 1KB is the same as 1024 x 8 = 8192 binary digits. Megabyte (MB): 1024KB equals one megabyte (MB). Gigabyte (GB): There are 1024MB in one gigabyte. Terabyte (TB): There are 1024GB in one terabyte (TB)
Why your hard drive has a lower capacity than advertised
Hard drive manufacturers have long eschewed the power-of-two system for the power of ten. Some say it’s a clever marketing ploy, but whatever the reason, it makes for some confusion depending upon which operating system you connect it to. Linux uses decimal these days, while Windows 10 uses power-of-two units. This means that 1000 Bytes = 1 kiloByte and 1000 kiloBytes = 1MB. Again, 1000MB = 1GB and 1000GB = 1TB. Windows sees a 250GB hard drive as 232GB, and a 1TB drive as 931GB. (The SSD above has an unusial capacity of 977GB, or 1049 Gibibytes.)
Usually a 1TB hard drive has the capacity to store 1,000,000,000,000 Bytes. Divide this by 1024 and you get 976,562,500KB. Divide by 1024 again and you get 953,674.3MB. Finally, divide by 1024 to get Gigabytes and you end up with 931.32GB. Remember too, that if a device – such as a phone or tablet – claims to have, say, 64GB of storage, that’s not the usable amount. That’s the total, and some of it will be used for the operating system and leave a lower amount available for you to use for apps, photos, videos and files.
Related articles for further reading:
CPU vs GPU: What’s the difference? What is a VPN How to know if a graphics card is compatible
Jim has been testing and reviewing products for over 20 years. His main beats include VPN services and antivirus. He also covers smart home tech, mesh Wi-Fi and electric bikes.
