File Size Converter (Bytes, KB, MB, GB, TB)

File Size Units: KB vs KiB, MB vs MiB

There are two competing standards for file size units — decimal (SI) and binary (IEC) — and the difference can cause significant confusion when comparing storage capacity to file size reports.

Decimal (SI) vs Binary (IEC)

• Decimal: 1 KB = 1,000 bytes | 1 MB = 1,000,000 bytes | 1 GB = 1,000,000,000 bytes
• Binary: 1 KiB = 1,024 bytes | 1 MiB = 1,048,576 bytes | 1 GiB = 1,073,741,824 bytes

Why Your Hard Drive Appears Smaller Than Advertised

Hard drive manufacturers advertise capacity in decimal (1 TB = 10¹² bytes = 1,000,000,000,000 bytes). Windows reports storage in binary GiB but labels them GB. A "1 TB" drive shows as ~931 GB in Windows because: 10¹²/2³⁰ = 931.3 GiB. This is not the manufacturer lying — it's a unit mismatch.

Which Units Do Systems Use?

• macOS: Uses decimal (1 GB = 10⁹ bytes) — storage appears closer to advertised
• Windows: Uses binary GiB but calls them GB — storage appears "missing"
• Linux: Uses binary (df -h shows GiB, though often labeled GB)
• Network speeds: Always decimal (100 Mbps = 100,000,000 bits per second)