FileSizeCalc

File Size, Storage & Transfer Calculators

Convert between KB, MB, GB and TB, estimate how long a download or backup will take, size a video before you export it, and work out how many photos, songs or hours of footage a drive really holds. Every calculator runs locally in your browser, shows its formula, and handles the awkward part honestly: 1024 versus 1000.

Guides

What these calculators do — and where the limits are

Solid ground

  • Unit arithmetic is exact: 1 GB is 1,000 MB decimal or 1,024 MB binary, and both results are shown.
  • Transfer times use the real formula — bits divided by bits per second — with a 90% efficiency row for planning.
  • File sizes are bitrate × time ÷ 8, the same maths encoders use, with codec factors stated on the page.
  • Capacity counts are whole files and include a conservative row that subtracts file-system overhead.

Where estimates meet reality

  • No connection runs at its headline rate: expect 90–95% on Ethernet and 50–80% over Wi-Fi.
  • Bitrate is an average — a static interview and a fireworks display at the same setting differ by 5×.
  • Cameras, phones and file systems add sidecar files and metadata that shave a few percent off every count.
  • We do not measure your hardware or your line speed. These pages do arithmetic on the numbers you enter, transparently.