Data Storage Converter
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Understanding Data Storage Units
Digital storage is measured in bytes, but there are two competing unit systems that cause frequent confusion: the binary system (powers of 1024, used by operating systems) and the SI decimal system (powers of 1000, used by hard drive manufacturers and storage specs).
SI vs Binary Prefixes
- SI (decimal, 1000-based): 1 KB = 1,000 bytes; 1 MB = 1,000,000 bytes; 1 GB = 1,000,000,000 bytes
- Binary (1024-based): 1 KiB = 1,024 bytes; 1 MiB = 1,048,576 bytes; 1 GiB = 1,073,741,824 bytes
- A "1 TB" hard drive contains 1,000,000,000,000 bytes but your OS shows ~931 GB due to 1024-based reporting
Common File Size References
- Typical email: 75 KB
- MP3 song (3 min): ~3–5 MB
- HD photo (JPEG): 2–5 MB; RAW photo: 20–30 MB
- 1080p movie (2 hours): 8–15 GB
- 4K movie (2 hours): 50–100 GB
Why does my 1TB hard drive show less space in Windows?
Hard drive manufacturers use SI (decimal) prefixes: 1 TB = 1,000,000,000,000 bytes. Windows uses binary prefixes: 1 TB displayed = 1,099,511,627,776 bytes. So a 1 TB drive contains 1,000,000,000,000 ÷ 1,099,511,627,776 ≈ 0.91 TB (or ~931 GB) in Windows. This is not missing storage — it's a unit system difference.
What is a petabyte?
1 petabyte (PB) = 1,000 terabytes (SI) = 1,000,000 gigabytes. To put it in perspective: 1 PB could store about 200,000 HD movies, or all the text of the U.S. Library of Congress about 50 times over. Major internet companies routinely store hundreds of petabytes. The next unit up is an exabyte (1,000 PB), which is the scale of global internet traffic per month.