💾 File Size: Calculator

Convert file size units, or estimate file size from bitrate and duration.

CONVERTED SIZE
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In Bytes
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In Bits
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Value × From-unit bytes ÷ To-unit bytes (binary, 1024-based)

How the File Size Calculator Works

This calculator has two modes. The Unit Converter mode converts a file size between bits, bytes, kilobytes, megabytes, gigabytes, and terabytes using the binary (1024-based) convention that operating systems typically use for file sizes. The Estimate from Bitrate mode works backward from a video or audio bitrate and duration to estimate the resulting file size, which is useful for planning recordings, downloads, or exports before you actually create the file.

Unit conversion: Bytes = Value × From-unit factor; Result = Bytes ÷ To-unit factor
Binary factors: 1 byte = 8 bits, 1 KB = 1024 bytes, 1 MB = 1024 KB, 1 GB = 1024 MB, 1 TB = 1024 GB
Bitrate estimate: File Size (MB) = Bitrate (kbps) × Duration (s) ÷ 8 ÷ 1024

Binary vs Decimal Units: Why 1 GB = 1024 MB Here

You may have noticed that a "1 TB" hard drive often shows up as roughly 931 GB in your operating system — that's because storage manufacturers typically use decimal (1000-based) units for marketing, while operating systems display file and drive sizes using binary (1024-based) units, sometimes labeled KiB/MiB/GiB in strict technical usage. This calculator uses the 1024-based convention throughout, matching what you'll see in Windows File Explorer, macOS Finder, and most file managers.

Estimating Size from Bitrate and Duration

Bitrate measures how many bits of data are used per second of audio or video, usually expressed in kilobits per second (kbps). Multiplying bitrate by duration gives total bits, dividing by 8 converts to bytes, and dividing by 1024 again converts to megabytes. This is the same core formula used by video editors and streaming platforms to estimate export file sizes before rendering, and is especially useful for figuring out whether a video will fit within an upload limit or storage device.

📎 Related Tools: Base Converter Calculator Audio Bitrate Calculator Video Bitrate Calculator Hash Generator

❓ Frequently Asked Questions

Why does this calculator use 1024 instead of 1000 for KB, MB, and GB?
This calculator uses the binary convention (1 KB = 1024 bytes) that operating systems like Windows and macOS use when reporting file and folder sizes, rather than the decimal convention (1 KB = 1000 bytes) sometimes used by storage manufacturers.
How do I estimate the size of a video before exporting it?
Switch to the 'Estimate from Bitrate' mode and enter your target export bitrate (in kbps) and the video's duration in seconds. The calculator applies File Size (MB) = Bitrate × Duration ÷ 8 ÷ 1024 to give you an estimated file size.
What's the difference between a bit and a byte?
A byte is made up of 8 bits. Storage sizes (file sizes, drive capacity) are almost always expressed in bytes and their multiples (KB, MB, GB), while data transfer speeds and bitrates are typically expressed in bits per second (like kbps or Mbps).
Can I use this calculator for download time estimates?
This tool calculates size and unit conversions, not download time directly. However, once you know a file's size in bits (shown in this calculator), you can divide by your connection speed in bits per second to estimate download time.
Why is my actual file slightly different from the estimate?
The bitrate estimate assumes a constant bitrate throughout the entire file. Many real video and audio files use variable bitrate (VBR) encoding, plus container overhead (metadata, headers), so actual file sizes are often close to but not exactly identical to this calculation.

🏆 About This Tool — Accuracy & Trust

🔒 Data Privacy: All calculations run entirely within your browser using JavaScript. Nothing you enter here is ever transmitted to our servers, stored, sold, or shared.

📐 Accuracy Note: This tool uses standard, widely published formulas and guidelines. Results are estimates for informational purposes; for financial, medical, or engineering decisions, consult a licensed professional.

📅 Last Updated: September 2026.