Definition

A kilobyte (KB) is a unit of digital information. In computing practice, 1 kilobyte is commonly treated as 1024 bytes. When manufacturers use decimal marketing, 1 kB may be listed as 1000 bytes. This calculator uses the binary convention by default (1 KB = 1024 bytes) and also lists binary-only units such as KiB/KiB, MiB, and GiB for clarity.

Origin or history

Early computers addressed memory in powers of two, so storage sizes naturally aligned to 2^10 = 1024. To reduce confusion between decimal and binary, the IEC introduced kibibyte (KiB) in 1998 for exactly 1024 bytes, while kilobyte (kB) stayed as 1000 bytes in SI contexts. Everyday operating systems and file managers, however, still commonly display 1 KB as 1024 bytes.

Current use

• Website image optimization: compress photos to 50–200 KB for faster page load.
• Email attachments: many providers show limits in MB, but small documents are measured in KB.
• Log files and CSV exports: individual rows are tiny; entire files are often just a few kilobytes.
• Embedded systems: firmware resources and text assets are budgeted in kilobytes.

Examples

• What is 1024 bytes in kilobytes? 1024 ÷ 1024 = 1 KB.
• How many KB are in 5 MB (binary)? 5 × 1024 = 5120 KB.
• Resize an image from 350 KB to under 150 KB for faster Core Web Vitals.
• Convert 750 KB to MB: 750 ÷ 1024 ≈ 0.732 MB.

Quick reference

• 1 Kilobyte = 1024 bytes
• 1 Megabyte = 1024 kilobytes
• 1 Gigabyte = 1024 megabytes
• 1 Terabyte = 1024 gigabytes