Video Bitrate Calculator
Hitting an Exact File Size Target When Exporting Video
Upload limits are a fact of life — a platform caps you at 8MB, 25MB, or some other ceiling, and the export bitrate has to be dialed in precisely enough to land under it without wasting quality on unnecessary headroom. Working that bitrate out by trial and error means repeated re-encodes; this calculator computes it directly from the target file size and duration, then subtracts out the audio track's share.
The Formula
The total available bitrate comes from spreading the target size evenly across the video's duration, then the audio portion is removed:
Video Bitrate (kbps) = Total Bitrate − Audio Bitrate
The 8192 factor converts megabytes to kilobits (1 MB = 1024 KB = 1024 × 8 kb = 8192 kb), so the result comes out directly in kbps once divided by duration in seconds.
Where This Calculation Matters
- Platform upload limits — hitting a hard cap like Discord's free-tier attachment limit or an email attachment size ceiling without over-compressing.
- Disc and physical media authoring — fitting a video onto a fixed-capacity format by working backward from the available space to a bitrate.
- Streaming and CDN cost control — capping average bitrate to manage bandwidth costs while still meeting a target file size per minute of content.
- Batch encoding consistency — computing a per-video bitrate so multiple clips of different lengths land at a similar predictable file size.
Bitrate Needed by Target Size and Duration
| Target Size | Duration | Total Bitrate | Video Bitrate |
|---|---|---|---|
| 8 MB | 1 min | 1,092.27 kbps | 964.27 kbps |
| 25 MB | 3 min | 1,137.78 kbps | 1,009.78 kbps |
| 100 MB | 10 min | 1,365.33 kbps | 1,237.33 kbps |
| 500 MB | 10 min | 6,826.67 kbps | 6,698.67 kbps |
If the audio bitrate exceeds the total available bitrate for a very small target size or short duration, there's no room left for video — increase the target size, extend the duration, or lower the audio bitrate.
How to Use This Calculator
- Enter the Target File Size (MB) you need to hit.
- Enter the Duration (minutes) of the video.
- Optionally set Audio Bitrate (kbps) — defaults to 128 kbps if left blank.
- Select Calculate to get the video bitrate to use in your export settings.
Related Calculations
Working with audio-only files instead? Use the Audio Bitrate Calculator. Need the reverse calculation — file size from a chosen bitrate? See the File Size Calculator.