Data Size Converter
Converts bytes, KB, MB, GB and TB in both decimal and binary conventions, and computes transfer times.
Converts between bytes, KB, MB, GB and TB in both the decimal and the binary convention, side by side, and works out how long a transfer takes at a given speed. It exists mainly to settle two arguments: why a 1 TB drive shows as 931 GB, and why a 100 Mbps line only moves 12.5 MB a second.
Size
Write it however you have it: 1.5 GiB, 1500MB, 1,024 KB, or a plain number of bytes.
The same number, both ways
decimal (SI, ×1000)
1 TB
what a manufacturer prints on the box
binary (IEC, ×1024)
931.32 GiB
what Windows shows and calls GB
At this scale the binary reading is 9.1% smaller. That is the whole of the "my 1 TB drive only has 931 GB" mystery: nothing is missing, the two systems just count differently and use overlapping names.
Every unit
| Unit | Value | System |
|---|---|---|
| B | 1,000,000,000,000 | ×1000 |
| KB | 1,000,000,000 | ×1000 |
| MB | 1,000,000 | ×1000 |
| GB | 1,000 | ×1000 |
| TB | 1 | ×1000 |
| PB | 0.001 | ×1000 |
| KiB | 976,562,500 | ×1024 |
| MiB | 953,674.316406 | ×1024 |
| GiB | 931.322575 | ×1024 |
| TiB | 0.909495 | ×1024 |
| PiB | 0.000888 | ×1024 |
Transfer time
time
22 hr, 13 min
How to use it
Type the size however you have it
1.5 GiB, 1500MB, 1,024 KB or a plain number of bytes all parse. The number itself is read the way this page’s language writes one: here the dot marks the decimal and the comma groups the thousands. On the pages whose language marks the decimal with a comma — Spanish, Portuguese, German, French, Italian — it is the other way round, and 1,5 GB is a gigabyte and a half there. Both readings come back out the same way, so what the tool prints is what it will take.
Read both conventions
Decimal is what a manufacturer prints on the box; binary is what Windows shows and calls GB. The gap between them is stated as a percentage.
Work out a transfer time
Give it a speed and it tells you how long. Note whether your figure is in bits or bytes — the difference is exactly eight.
Common questions
Where did the missing space on my 1 TB drive go?
Nowhere. The manufacturer counted 1,000,000,000,000 bytes and called it 1 TB; Windows divides by 1024 three times and calls the result 931 GB. Nothing is missing — the two systems count differently and use overlapping names.
What is the difference between MB and MiB?
MB is 1,000,000 bytes and MiB is 1,048,576. The IEC introduced the -bi- names in 1998 precisely to end this ambiguity, and almost nobody uses them, which is why the ambiguity is still here.
Why is my 100 Mbps line so slow?
It is not. A lower-case b is a bit and an upper-case B is a byte, and there are eight bits to a byte, so 100 Mbps is 12.5 MB per second at best. Confusing the two is off by exactly eight and is the most common wrong answer in this whole area.
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