Why 1KB Isn't Always 1,000 Bytes: Decimal vs. Binary Storage Units

This is one of the most persistently confusing unit conversions in computing, because two different standards have coexisted for decades — and almost nothing tells you which one it's using.

The Two Systems

Decimal (SI): 1 KB = 1,000 bytes, 1 MB = 1,000,000 bytes — used by storage manufacturers (hard drives, SSDs) and network speeds.

Binary (IEC): 1 KiB = 1,024 bytes, 1 MiB = 1,048,576 bytes — used by operating systems reporting file sizes and RAM.

Why This Matters Practically

It's the reason a "1TB" hard drive shows up as roughly 931GB in Windows File Explorer. The drive manufacturer used decimal (1TB = 1,000,000,000,000 bytes); Windows reports in binary (dividing by 1,024 repeatedly). Nothing is missing — it's two different definitions of the same word.

What Our Converter Handles

Bit ↔ Byte conversions (8 bits = 1 byte, always, no ambiguity there); KB/MB/GB/TB in both decimal and binary modes; and network speed conversions (Mbps vs MB/s — a very common mix-up, since network speeds are measured in bits, file sizes in bytes).

Common Mistake: Confusing Mbps with MB/s

Mbps (megabits per second) is used for internet speed. MB/s (megabytes per second) is used for file transfer/download size. Divide Mbps by 8 to estimate real-world MB/s — a "100 Mbps" connection tops out around 12.5 MB/s, not 100 MB/s.