File Size Converter

File sizes are stuck between two measurement systems and the resulting confusion costs the industry millions in customer-service tickets every year. The decimal system (SI prefixes: kilo, mega, giga) uses 1,000-byte units — what hard-drive manufacturers print on the box. The binary system (IEC prefixes: kibi, mebi, gibi) uses 1,024-byte units — what operating systems display when you check a file's properties. The two diverge by about 7% at the gigabyte scale and about 10% at the terabyte scale, which is why a "1 TB drive" appears in Windows as 931 GB. The drive isn't lying and Windows isn't lying — they're just measuring different things.

Where the 1024 came from

Computers are binary. Memory addresses, block sizes, page sizes, allocation units — all are powers of 2. 1,024 bytes (2^10) fits neatly into binary arithmetic; 1,000 bytes doesn't. So early computing (1950s-70s) treated 1 KB as 1,024 bytes for convenience. By the 1990s, hard drive manufacturers had a marketing motive to switch to 1,000 (the drives sound bigger that way), and standards bodies eventually formalised it: SI prefixes (KB, MB) for 1,000-based; IEC prefixes (KiB, MiB) for 1,024-based. In practice almost nobody outside Linux uses "KiB" — Windows displays a binary value but labels it "KB"; macOS at least switched to decimal "KB" with a true 1000-byte interpretation in 2009.

Which system does each thing use

Decimal (1000): hard drive labels, SSD labels, internet bandwidth (Mbps, Gbps), Cloud storage pricing (AWS S3, Google Cloud), Apple's macOS "About this Mac" storage display since 2009. Binary (1024): RAM sizes (always — "8 GB" of RAM is 8 GiB), Windows file/disk properties, Linux du/df output by default, file managers across most platforms. So a freshly-installed Windows reads your "1 TB" drive (1,000,000,000,000 bytes) as 931 GB (1,000,000,000,000 / 1,073,741,824). Both numbers describe the same physical drive.

Network speeds are bits, not bytes

Internet bandwidth uses bits per second (lowercase b), not bytes per second (uppercase B). So "100 Mbps" is 100,000,000 bits/second = 12.5 MB/s of usable file-transfer speed (8 bits per byte, with some overhead). A 1 Gbps line is theoretically 125 MB/s; protocol framing takes 5.07% of that (a full TCP/IPv4 segment carries 1,460 payload bytes per 1,538 bytes on the wire), leaving about 118.7 MB/s before any congestion, Wi-Fi loss or server-side limit — and those are usually the larger effect, but none of them follows from the plan rate. This is the source of many a "why does my fast internet download slowly?" question.

APAC storage and bandwidth context

Storage and bandwidth norms vary widely across APAC. Singapore sells 1 Gbps as a standard residential tier and 10 Gbps in some buildings, with Hong Kong, Japan, South Korea and Taiwan in the same bracket; Malaysia's tiers run from the low hundreds of Mbps upward; Indonesia, the Philippines and Vietnam are climbing from a lower base; and India spans the steepest range in the region, from urban fibre to single-digit Mbps in many rural areas.

No median figures are quoted here on purpose. National medians move monthly, and this page previously carried a set that contradicted the ones on our own data storage converter — two snapshots taken at different times, each stale soon after. Ookla's Speedtest Global Index is the source to read a current number from. What does hold steady is the thing this converter exists for: the factor of eight between the bits a line is sold in and the bytes a file is measured in, and the 1000-versus-1024 gap between what a drive is labelled and what an operating system reports. The "1 TB drive" is a regional commodity item, and the label-versus-OS mismatch confuses buyers region-wide.