The short version
Multiply total bitrate in bits per second by duration in seconds, then divide by eight to convert bits to bytes. Add video and audio bitrates before calculating.
What matters most
- Bitrate and duration determine an encoded file estimate more directly than resolution.
- Variable bitrate makes the result an estimate until encoding finishes.
- MB and MiB use different unit systems.
How to apply it
- Add video, audio and any relevant overhead bitrates.
- Convert duration to seconds.
- Multiply bitrate by seconds and divide by eight.
- Convert bytes to MB using 1,000,000 or MiB using 1,048,576, and label the result clearly.
Reference table
| Total bitrate | Duration | Approximate decimal size |
|---|---|---|
| 5 Mb/s | 1 minute | 37.5 MB |
| 10 Mb/s | 10 minutes | 750 MB |
| 20 Mb/s | 30 minutes | 4.5 GB |
| 50 Mb/s | 60 minutes | 22.5 GB |
Use exact dimensions and units in production notes; familiar labels can describe more than one standard.
Common mistakes to avoid
- Forgetting that bitrate is measured in bits while file size is usually bytes.
- Leaving audio bitrate out of the total.
- Assuming resolution alone predicts file size.
Continue with the right tool
Use a calculator to check the numbers against your own source and destination instead of relying on a generic preset.
Related guides
Video Resolution Chart: SD, HD, Full HD, 2K, 4K and 8K
Compare common video resolutions, pixel counts, aspect ratios and practical uses without confusing consumer UHD and cinema formats.
Video quality and delivery720p vs 1080p: Resolution, Pixel Count and File Size
Compare 1280×720 and 1920×1080 video, including pixel count, scaling, bandwidth and when each resolution makes sense.
Video quality and delivery1080p vs 4K: Pixels, Viewing Distance and Real-World Tradeoffs
Compare Full HD and 4K UHD by pixel count, display conditions, editing load, bitrate and storage before choosing a format.
Frequently asked questions
Why is the final file different from the estimate?
Variable bitrate, container overhead and encoder behavior change the actual total.
Does frame rate affect size?
It influences how much bitrate may be needed for a quality target, but bitrate remains the direct size input.
How many bits are in a byte?
Eight bits equal one byte.