Bits and bytes
A bit is a basic unit of digital information. A byte is made from eight bits and is commonly used as the starting point for describing file and storage sizes.
Decimal file-size units
Decimal units use powers of 1,000. They are widely used for storage capacities, networking and many general-purpose calculations.
- 1 kilobyte (KB) = 1,000 bytes
- 1 megabyte (MB) = 1,000 KB
- 1 gigabyte (GB) = 1,000 MB
- 1 terabyte (TB) = 1,000 GB
Binary file-size units
Binary measurement uses powers of 1,024. The IEC names for these units are kibibyte, mebibyte, gibibyte and tebibyte.
- 1 KiB = 1,024 bytes
- 1 MiB = 1,024 KiB
- 1 GiB = 1,024 MiB
- 1 TiB = 1,024 GiB
Why displayed storage can appear smaller
Differences between decimal manufacturer capacities and binary-style software reporting can make the displayed capacity look different even when the underlying number of bytes has not changed.
File size and download time
Larger files take longer to transfer at the same connection speed. To estimate transfer time, convert the file size and transfer rate to compatible units before dividing.
File size and storage planning
- Photos can range from small compressed files to large RAW images.
- Video file size varies significantly with resolution, bitrate, codec and duration.
- Compressed archives can be smaller than their uncompressed contents.
- Available disk space should include room for temporary files and application data.
When comparing capacities or performing conversions, confirm whether the values use decimal units such as GB or binary units such as GiB.