Data Size Converter

The converter covers both the decimal units on product boxes and the binary units some operating systems report.

1. Enter a number in the Value box, for example 1 or 250.
2. Pick the unit you have in From, such as Gigabyte (GB), and the unit you want in To, such as Gibibyte (GiB). The answer updates as you type.
3. Read the line under the result for the factor in both directions, then press Swap units to reverse them.
4. Check the In every unit list for the same amount in all ten units, from a bit to a tebibyte.

Use it to see why a drive shows less space than advertised, how a file in MiB compares with a plan quota in MB, or how big a download is in bytes. The calculation happens in your browser and nothing is sent anywhere. The converter accepts decimals and large values. The list has no petabyte unit and no per-second rates, so type megabits as bits, for example 100000000 for 100 Mb, or divide by 8 yourself.

A byte is 8 bits, and the confusion starts with the prefixes. Decimal units follow the metric system: 1 KB is 1,000 bytes, 1 MB is 1,000,000, 1 GB is 1,000,000,000 and 1 TB is 1,000,000,000,000. Binary units go up in powers of 2: 1 KiB is 1,024 bytes, 1 MiB is 1,048,576, 1 GiB is 1,073,741,824 and 1 TiB is 1,099,511,627,776.

Drive makers use decimal units. Windows divides by powers of 1,024 but still labels the result KB, MB and GB, while macOS reports decimal sizes. That is why a 1 TB drive appears as about 931 GB in Windows: 1,000,000,000,000 divided by 1,073,741,824 is 931.32. Type 1 with TB and GiB selected to see 931.3226. Nothing is missing; the unit is larger.

Internet speeds are sold in bits per second while files are measured in bytes, so the factor of 8 catches many people out. A connection of 100 Mbps moves 100 million bits per second, which is 12.5 million bytes or 12.5 MB per second. To estimate a download, convert the file to megabytes, multiply by 8 and divide by the speed in megabits per second.

• A 5 MB photo at 10 Mbps takes 4 seconds
• A 1 GB file at 100 Mbps takes 80 seconds
• A 50 GB game at 100 Mbps takes 4,000 seconds, about 67 minutes
• A 25 GB film at 500 Mbps takes 400 seconds, under 7 minutes

Real downloads usually run slower than these figures because of protocol overhead, wireless signal and shared bandwidth, so treat them as the most favourable case. A wired connection comes closer to the figure than a busy Wi-Fi network does. The time converter turns a long count of seconds into minutes and hours.

Reproduce these in the converter. A drive sold as 256 GB holds 238.4186 GiB, and 512 GB is 476.8372 GiB. A 4.7 GB single-layer DVD is 4.3772 GiB, and a 700 MB CD is 667.572 MiB. A 16 GiB memory module is 17.1799 GB. When a quota says 1 TB and your files add up to 931 GiB in a tool that reports binary units, you have used the whole allowance.

For text, remember that file size and character count are different. A plain English character takes one byte, but accented letters and emoji take two to four bytes each in UTF-8, so the character counter figure is a lower bound on size. If a file is too big for an upload form, the image compressor shrinks photos, and the number base converter helps when sizes are written in hexadecimal or binary.