Media Doctor · Free tool
Will this video fit? Enter its length and bitrate to estimate the file size, or enter a size limit to get the bitrate to export with. Audio and container overhead are included.
Runs in your browser. It only does arithmetic; no file is read or uploaded.
Windows apps from SteveShines
Compress, convert or trim a video without uploading it.
Compress, convert to MP4 and fix playback errors.
Video downloader and local media toolkit.
Cut video, remove silence and add captions.
Size (bytes) = (video bitrate + audio bitrate) × duration ÷ 8, with bitrates in bits per second and the duration in seconds. Containers such as MP4 and MKV add roughly 2%.
Not sure what bitrate or codec a file already uses? Check it with the Video Codec & Format Checker.
Add the video and audio bitrates, multiply by the duration in seconds and divide by 8 to get bytes. For example, 8 Mbps video plus 128 kbps audio for 10 minutes is (8,000 + 128) kbps × 600 s ÷ 8 ≈ 610 MB, plus about 2% for the container.
Multiply the limit in megabytes by 8,000 to get kilobits, divide by the duration in seconds, then subtract the audio bitrate and a few percent for the container. Choose “Which bitrate fits a size limit?” above and the calculator does this for you.
Most encoders use a variable bitrate, so simple scenes take less space and fast motion takes more. Expect the real size to land within about 10–20% of the estimate. Two-pass or constant-bitrate encoding gets closer to an exact size.
The calculator uses decimal megabytes (1 MB = 1,000,000 bytes), as most upload limits do. Windows Explorer counts 1 MB as 1,048,576 bytes, so it shows about 5% less. The result also lists the size in MiB, the unit Windows uses.
Around 8 Mbps is a common starting point for 1080p H.264 at 30 fps. HEVC (H.265) and AV1 reach similar quality at roughly half the bitrate. Screen recordings and slow scenes look fine with less; sports and games need more.
No. The calculator only does arithmetic in your browser and never reads a video file.