About the Data Size Converter
This data size converter handles both decimal units (KB, MB, GB, TB – powers of 1,000) and binary units (KiB, MiB, GiB, TiB – powers of 1,024), plus bits for network speeds. It also explains why a 1 TB drive appears as 931 GB in Windows and calculates the theoretical download time for any file size and connection speed.
How to use
- Type a size in the top box and choose its unit; pick the target unit below.
- Use the All / Decimal / Binary switch to show only the units you need.
- Enter the capacity printed on a drive to see what Windows will show.
- Enter a file size and your internet speed to estimate the download time.
Decimal vs. binary units
| Unit | Decimal (SI) | Binary (IEC) |
|---|---|---|
| 1 KB | 1,000 B | 1,024 B |
| 1 MB | 1,000 KB | 1,024 KiB |
| 1 GB | 1,000 MB | 1,024 MiB |
| 1 TB | 1,000 GB = 931.32 GiB | 1,024 GiB |
Mbps vs. MB/s
Internet plans are sold in megabits per second (Mbps), while browsers and download managers show megabytes per second (MB/s). One byte is 8 bits, so a 300 Mbps connection downloads at most about 37.5 MB/s.
FAQ
Is 1 GB 1,000 MB or 1,024 MB?
Officially 1 GB = 1,000 MB (decimal). 1,024 MiB make 1 GiB (binary). Windows shows binary values but labels them GB, which causes the confusion; macOS and drive makers use decimal.
Why does my 1 TB drive show 931 GB?
1 TB = 1,000,000,000,000 bytes. Windows divides by 1,073,741,824 (2³⁰) and gets 931.32, which it displays as “931 GB”. Formatting also uses a little space.
How long does it take to download 1 GB at 100 Mbps?
1 GB = 8,000 megabits, so 8,000 ÷ 100 = 80 seconds in theory. Real downloads are usually somewhat slower.