File Size Converter
Convert file sizes between bytes, KB, MB, GB, TB, and PB. Supports both decimal (SI) and binary (IEC) units: kilobytes vs kibibytes.
From Unit
= 1,024 bytes = 8,192 bits
Decimal (SI) — 1 KB = 1,000 B
Bytes (B)1,024
Kilobytes (KB)1.024
Megabytes (MB)0.001024
Gigabytes (GB)1.024e-6
Terabytes (TB)1.024e-9
Petabytes (PB)1.024e-12
Binary (IEC) — 1 KiB = 1,024 B
Bytes (B)1,024
Kibibytes (KiB)1
Mebibytes (MiB)9.766e-4
Gibibytes (GiB)9.537e-7
Tebibytes (TiB)9.313e-10
Pebibytes (PiB)9.095e-13
About File Size Converter
File sizes can be confusing because two competing systems exist: the decimal (SI) system where 1 KB = 1,000 bytes and the binary (IEC) system where 1 KiB = 1,024 bytes. Hard drive manufacturers use SI units (so a 1 TB drive has 1,000,000,000,000 bytes), while operating systems often report file sizes in binary units. A file shown as 1 GiB in Windows Explorer is 1,073,741,824 bytes, but a 1 GB measurement by a drive maker is only 1,000,000,000 bytes. This tool converts both ways so you can compare accurately.
Built and maintained by Meet Shah · Last updated
What this tool is used for
- Working out whether a file fits an upload limit quoted in different units.
- Converting a byte count from an API into something readable.
- Comparing a disk's advertised capacity against what an operating system reports.
- Sizing a transfer against a bandwidth budget.
- Converting a quota figure between decimal and binary units.
Frequently Asked Questions
- What is the difference between MB and MiB?
- 1 MB is 1,000,000 bytes; 1 MiB is 1,048,576. The IEC introduced the binary prefixes in 1998 to end the ambiguity, and the gap compounds — 2.4% at kilo, 4.9% at mega, 7.4% at giga, and about 10% by tera.
- Why does my 1 TB drive show as 931 GB?
- Because the manufacturer counted decimal and the operating system displays binary while still writing "GB". 10¹² bytes divided by 1024 three times is 931 GiB. Nothing is missing — two conventions are being used in one sentence.
- Which convention does each system use?
- Decimal for drive capacities, network speeds and macOS since 10.6. Binary for RAM always, for Windows file sizes, and for `ls -lh` by default. The mismatch between a download page and a file manager is the most common place people notice it.
- Why is RAM always binary?
- Because memory is addressed by a whole number of bits, so capacity is necessarily a power of two — there is no way to build a 1000-byte module. Storage has no such constraint, which is why only RAM is unambiguous regardless of which prefix is printed.
- Does file size mean bytes on disk?
- Not exactly. A filesystem allocates in blocks — commonly 4 KiB — so a 100-byte file occupies 4096 bytes of disk. That is why a folder of many tiny files consumes far more space than its reported total, and why `du` and `ls` disagree.
Common errors and gotchas
- Mixing decimal and binary prefixes, where a kilobyte may mean 1000 or 1024 bytes.
- Being surprised a drive shows less than advertised, which is this exact difference and not a fault.
- Confusing bits with bytes, a factor of eight that appears constantly in network figures.
- Rounding to whole megabytes near a hard limit, where the boundary is what matters.
- Comparing a compressed size against an uncompressed one as if they were the same measurement.
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