Data storage units measure digital information. From bytes to terabytes, understanding the difference between decimal (SI) and binary (IEC) prefixes is essential for accurately describing storage capacity.
The Byte: Foundation of Digital Storage
A byte is 8 bits. Each bit is a 0 or 1. A single character in ASCII takes 1 byte. The byte is the smallest addressable unit of memory in most computer architectures.
Decimal vs Binary Prefixes
Storage manufacturers use decimal (SI): 1 KB = 1,000 bytes, 1 MB = 1,000,000 bytes. Operating systems often use binary: 1 KiB = 1,024 bytes, 1 MiB = 1,048,576 bytes. This is why a "500 GB" drive shows ~465 GB in Windows.
- 1 KB (SI) = 1,000 B; 1 KiB (IEC) = 1,024 B
- 1 MB = 1,000 KB; 1 MiB = 1,024 KiB
- 1 GB = 1,000 MB; 1 GiB = 1,024 MiB
- 1 TB = 1,000 GB; 1 TiB = 1,024 GiB
Practical Storage Sizes
A plain text file: 1–100 KB. A photo (JPEG): 2–10 MB. A song (MP3): 3–10 MB. A movie (HD): 2–8 GB. A modern game: 50–150 GB. The entire Library of Congress text: ~10 TB.
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