Quick answer
Video size = (video + audio bitrate) × duration ÷ 8. A 5,000 kbps video with 128 kbps audio for 600 seconds is 0.3846 GB (0.3582 GiB).
Enter the video and audio bitrates and the duration. The calculator returns the file size.
Related tools: Audio File Size Calculator: File size of audio at a constant bitrate. Media File Size Calculator: File size of an audio or video stream from its bitrate and duration. Bitrate Calculator: Average bitrate of a file from its size and duration.
How to use the Video File Size Calculator
- Enter video bitrate (kbps) (above 0).
- Enter audio bitrate (kbps) (0 or more).
- Enter duration (s) (above 0).
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Video bitrate | A number, in kbps | > 0 |
| Audio bitrate | A number, in kbps | ≥ 0 |
| Duration | A number, in s | > 0 |
Formula and method
Formula
size = (video + audio bitrate) × duration ÷ 8
IEEE-754 double precision; shown to the decimals indicated.
Constant-bitrate estimate; container overhead adds a little.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Video bitrate = 5000; Audio bitrate = 128; Duration = 600.
| Result | Value |
|---|---|
| File size | 0.3846 GB |
| In GiB | 0.3582 |
Example 2
Inputs: Video bitrate = 12000; Audio bitrate = 192; Duration = 3600.
| Result | Value |
|---|---|
| File size | 5.4864 GB |
| In GiB | 5.1096 |
The first line is the headline result (file size). Below it the video File Size Calculator lists in GiB, which describe the same case from other angles. IEEE-754 double precision; shown to the decimals indicated.
Worked example
5,128 kbps × 600 s = 3,076,800 kbit, and ÷ 8 = 384,600 kB, about 0.385 GB.
Constant bitrate only
Variable-bitrate files vary around the average, and containers add overhead. An hour at the same bitrates would be about 2.3 GB.
How the result changes with video bitrate
Holding every other input at the first worked example, this table changes only video bitrate. It shows how sensitive the answer is to that one value; each row was produced by running this calculator.
| Video bitrate | File size | In GiB |
|---|---|---|
| 2500 | 0.1971 GB | 0.1836 |
| 5000 | 0.3846 GB | 0.3582 |
| 10000 | 0.7596 GB | 0.7074 |
| 20000 | 1.5096 GB | 1.4059 |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Video bitrate: entering "0" shows "Video bitrate must be greater than 0." beside that field and no result.
- Duration: entering "0" shows "Duration must be greater than 0." beside that field and no result.
Choosing between the Video File Size Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Audio File Size Calculator](/technology/audio-file-size-calculator/) | bitrate and duration | File size |
| [Media File Size Calculator](/technology/file-size-calculator/) | bitrate, bitrate unit and hours | File size |
| [Bitrate Calculator](/technology/bitrate-calculator/) | file size, size unit and duration | Average bitrate |
| [Playback Speed Calculator](/technology/playback-speed/) | hours, minutes and playback speed | New duration |
| [Screen Size Calculator](/technology/screen-size-calculator/) | diagonal, aspect ratio width and aspect ratio height | Screen size |
Background: networking and display
Network speeds are quoted in bits per second and file sizes in bytes, and a byte is 8 bits, so a 100 Mbps link moves at most 12.5 megabytes per second; real throughput is usually below the advertised rate. Pixel density is the diagonal in pixels divided by the diagonal in inches: a 1920×1080 display of 24 inches is about 92 pixels per inch, and a 3840×2160 display of 27 inches about 163.
Assumptions and limitations
- CBR only
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for video bitrate and duration to confirm this.
Frequently asked questions
What bitrate for 1080p?
1080p video often uses 4 to 8 Mbps for video, and 128 to 192 kbps more for audio.
How do I shrink a file?
Lower the bitrate or resolution.
Is audio included?
Yes, enter its bitrate.
What does the Video File Size Calculator calculate?
File size of video with audio at constant bitrates. It returns File size and In GiB.
What formula does the Video File Size Calculator use?
size = (video + audio bitrate) × duration ÷ 8. Constant-bitrate estimate; container overhead adds a little.
What do I need to enter in the video File Size Calculator?
You enter Video bitrate (kbps), Audio bitrate (kbps) and Duration (s).
How is the result rounded or limited?
IEEE-754 double precision; shown to the decimals indicated. CBR only.
What is an example of a video File Size result?
With video bitrate 5000, audio bitrate 128 and duration 600, the file size is 0.3846 GB.
Related calculators
- Audio File Size Calculator — File size of audio at a constant bitrate.
- Media File Size Calculator — File size of an audio or video stream from its bitrate and duration.
- Bitrate Calculator — Average bitrate of a file from its size and duration.
- Playback Speed Calculator — New duration and time saved at a faster playback speed.
- Screen Size Calculator — Width, height and area of a screen from its diagonal and aspect ratio.
- Download Time Calculator — Time to download a file at a given speed.
Sources
- SI prefixes (kB = 1,000 B) and IEC prefixes (KiB = 1,024 B); 8 bits per byte
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.