File Size Converter

File sizes are measured in bytes and their multiples. A byte is 8 bits — the smallest addressable unit of memory in most computer architectures. As files grow larger, we use kilobytes, megabytes, gigabytes, terabytes, and petabytes to express their size in human-readable form.

The confusion around file sizes stems from two competing standards: the decimal (SI) system where each unit is 1,000 times the previous, and the binary (IEC) system where each unit is 1,024 times the previous. This converter shows both side by side so you always know the exact value.

Computers operate in binary — powers of 2. Memory chips, caches, and registers are naturally sized in powers of 1,024 (2^10). Early computing adopted 'kilo' to mean 1,024 because it was close to 1,000. But as storage grew, the ~7% difference between 1,000 and 1,024 became significant. A '1 TB' hard drive that holds 1,000,000,000,000 bytes shows as only 931 GiB in a binary-reporting OS.

In 1998, the IEC introduced unambiguous binary prefixes: kibibyte (KiB), mebibyte (MiB), gibibyte (GiB), tebibyte (TiB), and pebibyte (PiB). Linux and macOS now use decimal units in their storage displays, while Windows still uses binary values labeled with decimal names — a persistent source of user confusion.

Understanding typical file sizes helps you estimate storage needs and download times. A plain text email is around 5 KB. A high-resolution JPEG photo is 3–5 MB. A 3-minute MP3 song is about 5 MB, while the same song in lossless FLAC might be 30 MB. A 1080p video averages about 1.5 GB per hour, and 4K video uses roughly 3 GB per hour.

For storage planning: a 256 GB phone can hold roughly 50,000 photos or 50,000 songs. A 1 TB external drive can store about 200 hours of 1080p video. Cloud storage tiers of 15 GB (free tier) hold about 5,000 photos or 3,000 songs.

Network speeds are measured in bits per second, not bytes. A 100 Mbps connection transfers 100 megabits — about 12.5 megabytes — per second. To convert download speed to file transfer time, divide the file size in megabytes by the speed in megabytes per second (Mbps ÷ 8).

This distinction matters when estimating download times. A 1 GB file on a 100 Mbps connection takes about 80 seconds in theory (1,000 MB ÷ 12.5 MB/s), though real-world overhead and latency typically add 10–20%. Understanding these conversions helps you plan uploads, backups, and data migrations accurately.