Data Storage Converter
Bytes, kilobytes, megabytes, gigabytes and terabytes, with the 1024-based units kept separate instead of quietly mixed in. Nothing is uploaded.
| Unit | Amount | Bytes each |
|---|
| Marked on the drive | Bytes | Windows shows |
|---|---|---|
| 256 GB | 256,000,000,000 | 238.42 GB |
| 500 GB | 500,000,000,000 | 465.66 GB |
| 1 TB | 1,000,000,000,000 | 931.32 GB |
| 2 TB | 2,000,000,000,000 | 1.82 TB |
| 4 TB | 4,000,000,000,000 | 3.64 TB |
Windows is dividing by 1024 and still writing GB. The figure in the middle column is what is actually on the drive, and it is exactly what was advertised.
How to use it
- Type the amount and pick the unit it is already in.
- The three tiles show the exact byte count and the same size read both ways — decimal and binary.
- The table lists every unit at once, so you never have to convert twice.
The 1000 against 1024 problem
Kilo means a thousand everywhere else in measurement, and that is what drive manufacturers use: a kilobyte is 1000 bytes, a megabyte is a million, a terabyte is a million million. Computers, meanwhile, address memory in powers of two, so the convenient round number in binary is 1024 rather than 1000.
For years both sizes were called a kilobyte, and the confusion is still with us. In 1998 the binary sizes were given their own names — kibibyte, mebibyte, gibibyte, tebibyte — so KiB could mean 1024 bytes and KB could go back to meaning 1000. This page keeps them as separate units in the list, because pretending they are the same thing is the whole source of the trouble.
The gap compounds. It is 2.4% at kilobytes, 4.9% at megabytes, 7.4% at gigabytes and about 10% by the time you reach terabytes. That last one is the missing 69 GB everybody notices on a new drive.
Why your new drive looks smaller than the box
A 1 TB drive holds 1,000,000,000,000 bytes, exactly as advertised. Windows divides that by 1024 four times, gets 931.32, and then writes “GB” next to it. Nothing has been lost and nothing has been taken by formatting — the same drive on macOS or Linux reads as 1 TB, because those count in thousands like the box does.
Bits and bytes are not the same letter
A byte is 8 bits. Storage is sold in bytes and written with a capital B; internet speed is sold in bits and written with a small b. So a 100 Mbps connection is 100 megabits a second, which is 12.5 megabytes a second at absolute best. A 1 GB file over a perfect 100 Mbps line takes about 80 seconds, not 10.
This catches people out in both directions, and the only clue in the writing is the case of one letter. Both are in the list above so you can see the factor of eight for yourself.
Frequently asked questions
Why does my 1 TB drive show as 931 GB?
Nothing is missing. The manufacturer counts a terabyte as 1,000,000,000,000 bytes, which is what the letters mean. Windows divides by 1024 four times instead, giving 931.32, but still labels the answer GB. The drive holds exactly what the box said; the two sides are using the same word for two different sizes. macOS and Linux count the same way as the box, which is why the same drive reads as 1 TB there.
What is the difference between KB and KiB?
A kilobyte is 1000 bytes and a kibibyte is 1024 bytes. The kibibyte, mebibyte and gibibyte were named in 1998 precisely so the 1024-based sizes could stop borrowing the SI prefixes. The gap starts at 2.4 percent for kilo and widens with every step, reaching about 10 percent by terabytes.
Is 100 Mbps the same as 100 MB per second?
No, and the difference is eight times. Internet speeds are quoted in megabits, written with a small b, while file sizes are in megabytes with a capital B. There are 8 bits in a byte, so a 100 Mbps connection downloads at about 12.5 MB per second at its very best.
Is anything I type sent anywhere?
No. The arithmetic happens in JavaScript inside your own browser. Nothing is uploaded and nothing is saved - close the tab and it is gone.