Data Storage Converter

A byte is 8 bits, and a bit is a single binary digit — one yes-or-no. Eight of them give 256 possible combinations, which was historically enough to encode one character of text, and the grouping stuck. From there each step up multiplies by 1024: 1 KB = 1,024 bytes, 1 MB = 1,024 KB, 1 GB = 1,024 MB, 1 TB = 1,024 GB. This converter uses that binary convention, which is how your operating system reports file and drive sizes. The 1,024 is not arbitrary — it is 2¹⁰. Computers address memory in powers of two, and 1,024 happens to be the power of two closest to 1,000, so the borrowed metric prefix "kilo" was near enough that nobody objected at the time. That decision is the source of essentially every storage-size argument since.

Two industries count the same bytes with two different rulers. Drive manufacturers use decimal, where 1 TB is exactly 1,000,000,000,000 bytes. Operating systems display binary, where a TB is 1,099,511,627,776 bytes. Nobody is lying and no space is missing — the drive holds every byte on the box. The label just gets divided by a bigger number before it is shown to you. Run the division and a "1 TB" drive reports as about 931 GB. A "500 GB" drive shows about 466 GB, and a "2 TB" drive shows about 1.82 TB. The gap widens at every rung, because the 2.4% difference compounds: 2.4% at KB, 4.9% at MB, 7.4% at GB, and 10% at TB. That is why the complaint barely existed in the floppy era and became universal once drives passed a terabyte. Platform behavior differs too — macOS switched to reporting decimal sizes, so it agrees with the packaging, while Windows still computes in binary and labels the result "GB".

The IEC settled this properly in 1998 by creating separate names for the binary quantities: kibibyte (KiB) = 1,024 bytes, mebibyte (MiB) = 1,024 KiB, gibibyte (GiB) = 1,024 MiB, tebibyte (TiB) = 1,024 GiB. NIST and the IEEE both endorse them. Under that scheme, KB/MB/GB revert to their plain metric meanings — 1,000, 1,000,000, 1,000,000,000 — and the ambiguity disappears entirely. A 1 TB drive is 1 TB and shows as 0.909 TiB, with no contradiction to explain. Adoption has been partial. Linux tooling and many technical specifications use the IEC units routinely; consumer software mostly does not, and Windows still writes "GB" for a quantity that is really GiB. So when a number matters, check which convention is in force — the "i" in the middle of the abbreviation is the tell.

This is the other factor-of-eight that costs people money. Internet service is sold in megabits per second (Mbps); files are measured in megabytes (MB). Eight bits to the byte, so the download speed you actually observe is roughly the advertised number divided by 8. A 100 Mbps connection tops out around 12.5 MB/s. A 1 Gbps fiber line delivers about 125 MB/s. A 300 Mbps plan is about 37.5 MB/s. None of this is throttling or false advertising — it is a unit conversion, and the real throughput is a little lower still because of protocol overhead. The notation carries the whole distinction in a single character: lowercase b means bit, uppercase B means byte. Mbps is megabits per second; MB/s is megabytes per second. When a speed test and a download manager appear to disagree by a factor of eight, that is what happened.

Rough working figures, useful for capacity planning: a compressed photo from a phone camera runs 2 to 5 MB; a RAW file from a mirrorless camera, 20 to 40 MB; a streaming-quality music track, 3 to 10 MB; an hour of 1080p video, roughly 1 to 3 GB; an hour of 4K, several times that. So a 128 GB phone holds something like 25,000 to 60,000 photos, or a few dozen hours of 4K footage — and rather less than that in practice, since the operating system and preinstalled apps claim a slice before you do. One useful asymmetry: memory is sold in binary units, storage in decimal. An 8 GB RAM module really is 8 GiB, which is why RAM capacities are always powers of two (4, 8, 16, 32) while drive capacities are round decimal numbers (500 GB, 1 TB, 2 TB). Memory has to map onto binary address lines; a hard drive does not, so its marketing department is free to use the friendlier number.