Kibibyte per second to Kibibit per second

Rsync follows IEC binary conventions because it deals with file sizes that are measured in binary units by the filesystem. Since files occupy whole filesystem blocks (typically 4 KiB), reporting transfer speed in KiB/s makes the math consistent with actual data moved on disk.

1 KiB/s (1,024 bytes/second) is 2.4% faster than 1 kB/s (1,000 bytes/second). The difference is tiny at this scale but matters when you are designing buffer sizes for embedded systems where every byte of RAM counts.

Microsoft started using binary units more consistently in Windows 10 after years of ambiguity where "KB" sometimes meant 1,000 and sometimes 1,024 bytes. The shift toward KiB follows IEC recommendations and reduces confusion, though the transition is still incomplete across all Windows tools.

A 3.5-inch floppy drive transferred data at about 31–62 KiB/s (250–500 kbps). Copying a full 1.44 MB floppy took roughly 25–50 seconds. For comparison, a modern NVMe SSD is about 100,000 times faster.

In embedded systems with tight memory constraints, confusing 1,024 with 1,000 can overflow a buffer. In network protocols, a spec written in KiB/s being implemented as kB/s means transmitting 2.4% less data than expected per second — enough to cause timing violations in real-time systems.

Because "kilo" was used to mean both 1,000 and 1,024 depending on context, causing real confusion. RAM manufacturers used 1,024 (binary) while network engineers used 1,000 (decimal). The IEC created kibi (Ki) in 1998 to unambiguously mean 1,024, leaving kilo for exactly 1,000.

Very few people outside of standards bodies and kernel developers. Linux kernel networking code sometimes uses binary units internally, and some IEC-compliant technical documents use Kibps. But consumer networking has fully standardized on decimal kilobits (kbps), making kibibits a niche pedantic distinction.

At the kibi/kilo level, only 2.4%. But the gap compounds — mebi vs mega is 4.86%, gibi vs giga is 7.37%, and tebi vs tera is 9.95%. A "1 TB" hard drive holds only 931 GiB in binary terms, which is why your new drive looks smaller than advertised in Windows.

Hard drives are built from sectors of arbitrary size, so decimal marketing (1 TB = 1,000 GB) is natural and makes drives look bigger. RAM is addressed in powers of 2 because of how binary memory chips work, so binary units (GiB) reflect actual hardware architecture. Neither side wants to change.

Almost certainly not. Networking adopted decimal (×1000) from the beginning because serial link speeds are clock-derived and have nothing to do with powers of 2. Ethernet has always been 10/100/1000 Mbps. Binary prefixes solve a storage problem that networking never had.