File Size Calculator
Convert between decimal units (KB = 1000 bytes) and binary units (KiB = 1024 bytes), and see how many files fit on a drive.
Convert file sizes between bytes, KB, MB, GB and TB in both decimal (1000) and binary (1024) units. See exactly why your 1 GB USB drive shows 931 MB — the difference between marketing and real units.
Units: SI decimal (1000) and IEC binary (1024) prefixes — both shown.
Convert a size
How many files fit on a drive?
How to use the File Size Converter
- Enter a size and pick the unit.
- See all equivalent values in decimal and binary units.
- Copy any value you need.
Frequently asked questions
Why does my 1 TB drive show 931 GB?
Drive makers use decimal units (1 TB = 1000 GB) while Windows reports binary units (1 TiB = 1024 GiB), so the same bytes show a smaller number.
What is the difference between MB and MiB?
MB = 1,000,000 bytes (decimal); MiB = 1,048,576 bytes (binary). This tool shows both.
How many bytes in a kilobyte?
1000 bytes in a decimal kilobyte, 1024 bytes in a binary one — it depends on the convention in use.
How do I convert KB to MB?
Enter the value in KB and read the MB row — done instantly.