Tip: Presets fill typical values. You can still edit all fields manually.
How this video format size calculator works
This calculator estimates video file size using the most important variables: duration, video bitrate, audio bitrate, and container overhead. It is useful for planning uploads, storage, backups, streaming budgets, and export settings.
Unlike guesswork, bitrate-based sizing gives you predictable results across formats such as MP4, MKV, MOV, AVI, and WebM. If you already know your target bitrate, this method is accurate enough for most production workflows.
The core formula
The estimate is based on this formula:
File Size = (Video Bitrate + Audio Bitrate) × Duration × (1 + Overhead)
- Bitrate is measured in kilobits per second (kbps).
- Duration is measured in seconds.
- Overhead accounts for container metadata and muxing structure.
In practice, final files can vary slightly due to variable bitrate behavior, subtitle tracks, chapter markers, metadata, and encoder implementation.
Container format vs codec: why both matter
Container format (MP4, MKV, MOV, etc.)
The container organizes streams (video, audio, subtitles, metadata). It does not define compression quality by itself. Container choice mainly affects compatibility and a small overhead percentage.
Codec (H.264, H.265, VP9, AV1, ProRes)
The codec determines compression efficiency. Newer codecs (H.265, AV1) usually produce smaller files at similar quality compared to H.264. Editing codecs such as ProRes prioritize quality and performance over small size.
| Use Case | Typical Codec | Common Bitrate Range |
|---|---|---|
| Mobile / Social 720p | H.264 | 1,500 - 3,500 kbps |
| 1080p Streaming | H.264 / VP9 | 4,000 - 8,000 kbps |
| 4K Distribution | H.265 / AV1 | 12,000 - 35,000 kbps |
| Editing Masters | ProRes / DNxHR | 100,000+ kbps |
Example calculations
Example 1: 10-minute 1080p MP4
- Video bitrate: 8,000 kbps
- Audio bitrate: 192 kbps
- Duration: 600 seconds
- Overhead: 1.5%
Result is roughly 620 MB (decimal). This is a common range for good-quality H.264 uploads.
Example 2: Same duration in H.265
If quality is matched but bitrate drops to around 5,000 kbps video, file size can decrease substantially. This is why codec selection matters as much as resolution.
How to reduce video file size without destroying quality
- Use a more efficient codec (H.265, VP9, or AV1 when supported).
- Lower bitrate gradually and compare visually, not just numerically.
- Use two-pass encoding for distribution exports.
- Reduce frame rate if motion does not require high fps.
- Downscale resolution when delivery platform or audience does not need 4K.
- Keep audio bitrate appropriate (128-192 kbps is often enough for spoken content).
Practical planning tips
For creators and teams, size forecasting helps avoid failed uploads, overage costs, and storage surprises. Before batch exports, calculate one representative file, verify actual output, then scale your estimate by project count.
If you archive source masters, expect dramatically larger files than delivery versions. Keep separate storage tiers for raw footage, edit intermediates, and final distribution renders.
Quick FAQ
Is this exact?
It is an estimate and usually very close for CBR workflows. VBR outputs may vary.
Why show both MB and MiB?
Storage vendors often use decimal units (MB/GB), while many operating systems report binary units (MiB/GiB).
What overhead should I use?
For most MP4 files, 1-2% is a solid default. Use higher values for formats with heavier muxing overhead.