Understanding Digital Storage Units: Decimal (SI) vs Binary (IEC) Standards
Quantifying data in computer science involves a dual mathematical framework: the decimal (base 10) standard from the International System of Units (SI) and the binary (base 2) standard defined by the International Electrotechnical Commission (IEC). Grasping this distinction is critical for software architects configuring database sharding limits, cloud bucket ingress limits, and API multipart upload thresholds.
1. SI Decimal (Base 10) vs IEC Binary (Base 2) Comparison
| SI Unit (Decimal) | Byte Value | IEC Unit (Binary) | Byte Value |
|---|---|---|---|
| 1 KB (Kilobyte) | 1,000 bytes (10^3) | 1 KiB (Kibibyte) | 1,024 bytes (2^10) |
| 1 MB (Megabyte) | 1,000,000 bytes (10^6) | 1 MiB (Mebibyte) | 1,048,576 bytes (2^20) |
| 1 GB (Gigabyte) | 1,000,000,000 bytes (10^9) | 1 GiB (Gibibyte) | 1,073,741,824 bytes (2^30) |
| 1 TB (Terabyte) | 10^12 bytes | 1 TiB (Tebibyte) | 2^40 bytes |
2. Why Does a 1 TB Drive Show As 931 GB in Windows?
Hard drive and SSD manufacturers manufacture devices using metric base 10 (1 TB = 1,000,000,000,000 bytes). Microsoft Windows measures disk sectors in binary increments of 1,024 bytes (GiB), but displays the metric label 'GB': 1,000,000,000,000 / (1,024^3) ≈ 931.32 GiB. The drive contains all promised bytes — only the display unit differs!