Guide
About this file size converter
Type a size once and read it in every unit at once: decimal SI units (bytes, KB, MB, GB, TB, PB — powers of 1,000) on one side and binary IEC units (KiB, MiB, GiB, TiB, PiB — powers of 1,024) on the other. Results update live as you type, each value has its own copy button, and the Random Size button loads familiar reference objects — a CD at 700 MB, a DVD at 4.7 GB, a 1 TB hard drive — to sanity-check magnitudes.
How to use the file size converter
- 1.Enter a number and pick the unit it is measured in, from bytes up to pebibytes.
- 2.Read the equivalent decimal (SI) and binary (IEC) values side by side.
- 3.Copy any individual result with its copy button.
- 4.Use Random Size to load the typical size of a real-world object for comparison.
Important details
Why your 1 TB drive shows 931 GB
Drive manufacturers sell capacity in decimal units: 1 TB = 1,000,000,000,000 bytes. Operating systems report binary units: 1,000,000,000,000 ÷ 1,073,741,824 ≈ 931 GiB — often displayed with the wrong “GB” label. No capacity is missing; the two unit systems simply differ by about 7.4% at terabyte scale.
KB versus KiB in practice
Memory is always binary — 16 GiB of RAM is 2^34 bytes. Network bandwidth is decimal and measured in bits: 100 Mbps is 100,000,000 bits per second, roughly 11.9 MiB/s of real transfer. Storage marketing is decimal; OS file dialogs are usually binary. When a number matters, write the exact unit.
The 1,000 versus 1,024 gap grows with scale
At kilobyte scale the difference between the systems is 2.4%, at gigabyte scale 7.4%, and at terabyte scale about 10%. The bigger the numbers, the further the two systems drift — which is why ambiguous units cause real capacity-planning bugs.
Frequently asked questions
How many bytes are in a megabyte?
In SI units, 1 MB = 1,000,000 bytes. In IEC binary units, 1 MiB = 1,048,576 bytes (1,024 × 1,024). The converter shows both so you never have to guess which one a tool or spec meant.
Should my code use 1,000 or 1,024?
Match the domain: memory and OS-level sizes are conventionally binary (1,024); storage devices and networks are decimal (1,000). Document whichever you choose — an ambiguous “MB” has caused many off-by-7% bugs.
What comes after terabytes?
Decimal: petabytes (PB), exabytes (EB), zettabytes (ZB). Binary: pebibytes (PiB), exbibytes (EiB), zebibytes (ZiB). This converter covers bytes through PB and PiB.
References: NIST: prefixes for binary multiples