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 over 12% 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). Singapore's 1 Gbps home broadband is theoretically 125 MB/s; in practice you'll see 100-110 MB/s due to TCP overhead and ISP shaping. 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 offers 1 Gbps (and 10 Gbps in some buildings) standard home broadband — the fastest residential connectivity in the world. Japan and South Korea match this. Hong Kong is similar. Malaysia's average home connection is 100-500 Mbps; Indonesia and the Philippines average 50-100 Mbps; Vietnam is improving rapidly through the 100-300 Mbps range. India ranges from 50 Mbps urban fiber to single-digit Mbps in many rural areas — the steepest spread in the region. Australia's NBN reached 1 Gbps in many premises in 2024 but the average is closer to 100 Mbps. China is the largest mobile-broadband market with significant 5G deployment but home wired fiber speeds typically sit around 200-500 Mbps. Taiwan, particularly Taipei, has near-universal 500 Mbps to 1 Gbps fiber. The "1 TB drive" is now a regional commodity item — under USD 60 anywhere in APAC. Hard-drive vs operating-system size mismatch confuses users region-wide.