Try the calculator
Runs in your browser. No signup, upload or saved inputs.
When this is useful
A bitrate budget helps you choose a starting encode, but it does not tell you whether the interface will remain readable. Duration and source complexity still need editorial and visual review.
How to use this calculator
- Enter a target size in decimal MB and the intended duration in seconds. Use a budget below any hard upload ceiling to leave room for overhead.
- Enter audio bitrate in kbps. The calculator subtracts its estimated payload from the total before calculating video Mbps.
- If no video budget remains, reduce duration or audio needs, or increase the size budget. Otherwise, test a short encode at the calculated bitrate and inspect text and motion.
Worked calculation
An illustrative 30 MB media budget over 60 seconds permits 4 Mbps in total. After reserving 128 kbps for audio, the estimated video budget is 3.872 Mbps. Container overhead would require additional headroom.
Formula and units
Video Mbps = target MB × 8 ÷ seconds − audio kbps ÷ 1000.
Limits and checks
The tool rejects a budget that is entirely consumed by audio. It does not predict constant-quality encoding size or guarantee a particular visual quality. Use the actual final file for the acceptance check.
Your next step
Compare the estimated bitrate with a representative export and shorten or reframe the story if the available detail is insufficient.
Frequently asked questions
How do I calculate audio bitrate from file size?
Audio kbps = file size in MB × 8,000 ÷ duration in seconds. A 1.92 MB audio track that lasts 120 seconds averages 128 kbps. Use decimal megabytes (1 MB = 1,000,000 bytes) and treat the result as an average, because variable-bitrate files and container metadata move it slightly.
How much space does audio take in a video file?
Audio MB = audio kbps × seconds ÷ 8,000. At 128 kbps, one minute of audio is about 0.96 MB; at 192 kbps it is about 1.44 MB; at 320 kbps it is 2.4 MB. The calculator subtracts this audio share from your size budget before it works out the video bitrate.
What audio bitrate should I use for a product demo or screen recording?
For voice-over and light music in a web video, 128 kbps AAC stereo is a common, safe starting point, and 96 kbps is often enough for speech alone. Use 192 kbps or more when music carries the piece. Listen to the actual export on laptop speakers and headphones before you lock it.
Can I use this as an audio-only bitrate calculator?
Yes, for a size budget. Set the audio field to 0 and read the total bitrate line: that is the average bitrate, in Mbps, that fits the size and duration you entered. Multiply by 1,000 for kbps. For example, 5 MB over 300 seconds allows about 133 kbps.
Why is my exported file bigger than the calculator says?
The estimate covers the media streams only. Container overhead, metadata, cover art and variable-bitrate peaks add to the final size, and some encoders overshoot a target bitrate on short clips. Keep a few percent of headroom below any hard upload limit and check the real file.
References and scope
Examples are illustrative production guidance, not measured customer results. General workflows are not promises of product compatibility. Read our editorial approach and current Demovela scope.