About FileSize.org

What this site covers

FileSize.org is a small, single-purpose reference site built around four kinds of file-size questions readers run into every day:

• Unit conversions — bytes, kilobytes, megabytes, gigabytes, terabytes, petabytes, plus bit-rate units like Mbps and MB/s. Each pair has its own page with binary (1024) and decimal (1000) modes.
• Platform upload limits — current per-file caps for messaging, email, video, and cloud-storage services. Each page lists the free-tier and paid-tier limit alongside a short note on workarounds.
• Media calculators — estimates for video, audio, and image file sizes from inputs like resolution, bit rate, sample rate, and duration. There are also planners for storage capacity and transfer time.
• Compression guides — practical, format-by-format walkthroughs for shrinking PDFs, video, audio, and images without destroying quality.

Editorial approach

The site is a reference, not a blog. Every page is designed to answer one specific question with the smallest amount of reading required: a working tool at the top, a short explanation underneath, and the formulas, examples, and caveats below that for readers who want to verify the result.

Conversion formulas are the standard ones used across the industry — powers of 1024 for binary units (KiB, MiB, GiB) and powers of 1000 for the decimal/SI units storage manufacturers print on their packaging. Both are exposed in the converters because both are correct in different contexts, and confusing them is one of the most common reasons readers end up here.

Platform limits change. The numbers shown on the limits pages reflect the publicly documented caps at the time of the most recent review for each page. When a service publishes new tiers or changes its policy, the page is updated. If you spot an outdated figure, the contact page lists the best way to flag it.

How content is produced

Pages are written and maintained by the site's small editorial team. Conversion math is verified against the unit definitions published by the IEC and NIST. Platform-limit figures are sourced from each provider's official help center or developer documentation, with the URL noted in the page source so future reviews can confirm the figure has not moved.

Compression guides are walked through on real files before publication — the commands, settings, and percentage savings shown in each guide reflect actual runs on representative source material. When a technique only helps in narrow cases, the guide says so.

How the tools work

Every converter and calculator runs entirely in your browser using JavaScript. Nothing you type is sent to a server, because there is nothing on the server side that would do anything with it — the math is simple enough to do client-side, and that is faster than a round trip anyway.

This is also the reason there is no upload feature, no account system, and no “save your last result” history. The site does not keep state for you.

How the site is funded

FileSize.org displays advertising provided by Google AdSense. Ads pay for hosting, domain renewal, and the ongoing time required to keep the platform-limit pages current. The site does not sell data, run affiliate schemes, or charge for any of its tools, and it has no paid tier.

For details on the cookies and identifiers used by the ad system, see the cookies page. For everything else, see the privacy policy.

Get in touch

Corrections, suggestions, and bug reports are all welcome. The contact page lists the email address to use.