What it is
The Data Size Converter moves between bits, bytes, kilobytes, megabytes, gigabytes and terabytes, and shows both conventions in use.
Why your 1 TB drive shows up as 931 GB
Nothing is missing and nobody cheated you. Two different definitions are in play at once.
The manufacturer counts in decimal: 1 TB means a trillion bytes, because kilo, mega and tera have meant powers of a thousand since long before computers existed.
The operating system counts in binary: 1 TB means 1,099,511,627,776 bytes, because memory is addressed in powers of two and 1,024 is the nearest round number to a thousand in that world.
Divide the first by the second and you get 0.909. Hence 931 GB, which is exactly the same bytes described with a different ruler. The gap widens as the numbers grow: it is 2.4% at kilobytes and nearly 10% at terabytes.
The MB and Mb trap
A capital B is bytes. A lowercase b is bits. There are eight bits in a byte, and the difference costs people money.
Internet plans are sold in bits per second because the number looks bigger. A 100 Mb/s connection downloads at about 12.5 MB/s at best. When someone complains that their 300 Mb plan only downloads at 37 MB/s, the plan is working perfectly.
Sizing things in practice
- A phone photo is usually 3 to 5 MB, so a 64 GB card holds somewhere around 15,000 of them.
- A raw file from a professional camera can be 50 MB, bringing that same card down to about 1,300.
- An hour of streamed video runs from roughly 1 GB at standard definition to 7 GB or more at 4K, which is why data caps disappear so fast.
How to use it
Pick both units, type the number, and read the result in decimal and binary side by side.