Kilobyte to Exbibyte

In the SI decimal system (used by storage manufacturers), 1 kB = 1,000 bytes. In the older binary convention (used by operating systems and programrs), what was called a "kilobyte" was actually 1,024 bytes — now formally called a kibibyte (KiB). The IEC standardized the KiB prefix in 1998 to eliminate this ambiguity. Modern OS versions (Windows Vista+, macOS 10.6+) increasingly use the correct IEC binary prefixes for displayed values.

One kilobyte (1,000 bytes) can store approximately 1,000 ASCII characters, roughly half a page of plain text, or about 140–170 words. With UTF-8 encoding, common English text is still close to 1 byte per character. A full page of formatted text with some HTML markup is typically 3–6 kB.

Storage manufacturers measure 1 kB = 1,000 bytes (decimal). Operating systems traditionally reported 1 kB = 1,024 bytes (binary). A drive advertised as 1 TB (1,000,000,000,000 bytes by the manufacturer) shows as approximately 931 GiB in Windows — not a lie, but a different counting system. The IEC binary prefixes (KiB, MiB, GiB) were introduced in 1998 to clarify this, and most modern OSes now use them correctly.

Files under 1 MB are typically measured in kilobytes: text files (1–100 kB), favicons and tiny images (1–50 kB), simple HTML pages (10–200 kB), audio samples (under 1 second of compressed audio), configuration and log files. Once files exceed a few hundred kilobytes they are more conveniently expressed in megabytes.

Early email systems in the 1980s–90s imposed attachment limits of 50–100 kB due to tiny disk quotas and slow dial-up links. As infrastructure improved, limits rose: most modern email providers (Gmail, Outlook) cap attachments at 25 MB. The limits persist because email traverses multiple relay servers (MTAs), each with its own size constraint, and Base64 encoding inflates binary attachments by ~33%. Some corporate and government systems still enforce 5–10 MB limits for security scanning and archival compliance. For larger files, email providers redirect to cloud links (Google Drive, OneDrive) rather than raising the attachment ceiling.

EB (exabyte) = 10¹⁸ bytes (SI decimal). EiB (exbibyte) = 2⁶⁰ bytes = 1,152,921,504,606,846,976 bytes (IEC binary). EiB is 15.29% larger. This is the largest practically significant SI vs IEC discrepancy: per exbibyte, the binary value exceeds the decimal value by approximately 152,921,504,606,846,976 bytes — about 152.9 petabytes.

One exbibyte (EiB) ≈ 1.153 × 10¹⁸ bytes = 1,073,741,824 GiB = 1,048,576 TiB. In practical terms: enough to store approximately 230 billion JPEG photos at 5 MB each, or 288,230,376 copies of a 4 GB HD movie, or the entire text content of the English internet many thousands of times over.

In theory, yes — and with astonishing density. DNA can encode about 215 PiB per gram of material, meaning a single EiB could fit in roughly 4.7 grams of synthetic DNA. Researchers at Microsoft and the University of Washington have demonstrated writing and reading megabytes of data in DNA strands. The challenges are speed and cost: current DNA synthesis writes about 400 bytes per second and costs around $3,500 per megabyte. At that rate, writing 1 EiB would take billions of years and cost more than global GDP. However, enzymatic synthesis breakthroughs could reduce costs by 6–8 orders of magnitude within decades.

Storing 1 EiB on modern HDDs would require roughly 57,000 drives of 20 TB each, consuming about 400–500 kW of power just for the drives — plus 200–300 kW for cooling, networking, and overhead. That totals roughly 6 GWh per year, equivalent to powering about 550 US homes. At typical US grid carbon intensity, this produces around 2,500 tonnes of CO₂ annually. Hyperscale operators reduce this via renewable energy and immersion cooling, but the fundamental physics of spinning magnetic platters or maintaining NAND charge states sets a floor on energy consumption that no software optimisation can eliminate.

After exbibyte (EiB, 2⁶⁰ bytes) come: zebibyte (ZiB, 2⁷⁰ bytes) and yobibyte (YiB, 2⁸⁰ bytes), as defined in IEC 80000-13. These are recognized standard units but have no current practical applications. The entire global internet's estimated stored data (hundreds of EB) is still in the low hundreds of EiB range — well short of one ZiB.