File Size Converter (Bytes to KB/MB/GB)
A file size converter that converts between bytes, KB, MB, GB, and TB using both decimal (base-10) and binary (base-2) systems. Ever wonder why your 500 GB hard drive shows as 465 GB in Windows? It's because storage vendors use decimal units (1 KB equals 1,000 bytes), while operating systems use binary units (1 KiB equals 1,024 bytes). This tool clarifies the difference and shows exact conversions in both systems. Developers use this to calculate bandwidth requirements, estimate download times, and debug storage allocation issues. System administrators use it to understand capacity discrepancies between vendor specs and OS reporting. Students use it to learn the difference between kilobytes and kibibytes. This tool converts any value in bytes, KB, MB, GB, or TB to all other units instantly, with copy buttons for each result. Toggle between decimal and binary modes to see how the same file size is reported differently. Free, no signup, works offline, and all calculations happen in your browser.
Decimal (Base-10) Results
Decimal (Base-10): 1 KB = 1,000 bytes. This is how storage vendors measure capacity (e.g., a 500 GB hard drive).
How to Use This File Size Converter
- Choose Decimal or Binary mode at the top (decimal for storage vendors, binary for OS file sizes)
- Enter a file size value and select its unit (bytes, KB, MB, GB, or TB)
- See instant conversions to all other units in the results table below
- Copy any result by clicking the copy button next to each value
- Switch modes to see how the same file size is reported in the other system
Why File Size Confusion Exists
The confusion between KB vs KiB stems from two competing standards. In decimal (base-10), 1 KB equals exactly 1,000 bytes, following the metric system (kilo means 1,000). In binary (base-2), 1 KiB equals 1,024 bytes because computers use powers of 2 (2^10 equals 1,024). Hard drive manufacturers use decimal units to advertise capacity, so a 500 GB drive is 500,000,000,000 bytes. But when you plug it into Windows, the OS uses binary units, so it shows as 465.66 GiB (500,000,000,000 ÷ 1,073,741,824). This isn't false advertising; it's a difference in unit definitions.
The IEC standard (International Electrotechnical Commission) introduced binary prefixes in 1998 to resolve this ambiguity: KiB (kibibyte), MiB (mebibyte), GiB (gibibyte), and TiB (tebibyte) for binary, and KB, MB, GB, TB for decimal. However, most operating systems still display 'GB' when they mean 'GiB', perpetuating the confusion. Linux uses GiB notation in some tools, but Windows and macOS display GB for binary units.
Developers need accurate file size conversions for API responses, database storage planning, and bandwidth calculations. For example, if your API returns file sizes in bytes (e.g., Content-Length: 5242880), you need to convert it to a human-readable format like 5 MB (decimal) or 5 MiB (binary). Network engineers use decimal units for bandwidth (a 100 Mbps connection transfers roughly 12.5 MB per second), while storage is measured in binary. This tool eliminates manual calculation errors and ensures you're using the right unit system for your context.