The KB vs. KiB Discrepancy, Explained
This is a genuinely common source of "why does my file show a different size in two places" confusion: decimal units (KB, MB, GB) use powers of 1,000 per the SI standard (1 KB = 1,000 bytes), while binary units (KiB, MiB, GiB) use powers of 1,024 (1 KiB = 1,024 bytes) — two different, both legitimate, definitions that happen to use confusingly similar abbreviations.
Storage manufacturers conventionally advertise capacity using decimal units (a "1 TB" drive means 1,000,000,000,000 bytes), while operating systems have historically displayed file and drive sizes using binary units while mislabeling them with decimal unit names (showing "GB" when the actual calculation used 1,024-based math) — which is exactly why a drive labeled "1 TB" shows up as roughly 931 "GB" in an OS that's actually computing gibibytes but displaying the wrong unit label. This isn't a manufacturing defect or missing storage; it's two different, both mathematically correct, definitions colliding under an ambiguous shared abbreviation.
The gap between decimal and binary units grows with scale — it's negligible at the kilobyte level (2.4% difference) but compounds to nearly 10% by the terabyte level, which is exactly why the discrepancy becomes noticeable and confusing specifically for large modern drives, not for small file sizes where the difference is easy to overlook.