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File Size Calculator

Convert any file size between bytes, kilobytes, megabytes, gigabytes and terabytes. Both binary (1024-based, the way Windows shows sizes) and decimal (1000-based, the way drive manufacturers label disks) are shown side by side.

UnitBinary (1024)Decimal (1000)

Binary vs decimal: why your 1 TB drive shows as 931 GB

Storage manufacturers measure capacity in decimal units (1 KB = 1000 bytes), but most operating systems display files in binary units (1 KiB = 1024 bytes). The two diverge as sizes grow:

  • 1 GB (decimal) = 1,000,000,000 bytes
  • 1 GiB (binary) = 1,073,741,824 bytes — about 7.4% larger

That is why a "1 TB" hard drive is shown as 931 GiB in Windows, and why a 4 GB file won't fit on a USB stick labelled "4 GB" formatted FAT32.

How to estimate transfer time

Internet speeds are measured in megabits per second (Mbps), but file sizes are in megabytes (MB). 1 byte = 8 bits, so divide your Mbps by 8 to get MB/s. Want a one-click estimate? Try our transfer speed calculator.