kbit/s × time ÷ 8 = size
Video bitrate calculator
A 10-minute video at 5000 kbit/s with 128 kbit/s audio holds 384.6 MB of data. Enter a bitrate and a length to get the size, or a size limit to get the bitrate.
- 5000 + 128 kbit/s × 10:00 = 384.6 MB
- 25 MB ÷ 3:00 − 128 kbit/s = 983.1 kbit/s
Both calculators update as you type. Sizes count the audio and video data only: the file will be slightly larger once the container is added, so keep a small margin below any hard limit.
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At a glance
- Price
- No charge
- Account
- None needed
- Upload
- Not applicable — you type numbers, nothing is sent anywhere
- Formula
- (video + audio kbit/s) × 1000 × seconds ÷ 8 = bytes
- Units
- 1 kbit = 1000 bits; MB and GB in powers of 1000, MiB and GiB in powers of 1024
- Limit
- Audio and video data only; container overhead is not included
Video size at common bitrates
These figures use the same formula as the calculator, for video only. Add the audio bitrate to the video bitrate before you multiply.
| Video bitrate | Per minute | Per hour |
|---|---|---|
| 1000 kbit/s | 7.5 MB | 0.45 GB |
| 2500 kbit/s | 18.75 MB | 1.125 GB |
| 5000 kbit/s | 37.5 MB | 2.25 GB |
| 8000 kbit/s | 60 MB | 3.6 GB |
| 16000 kbit/s | 120 MB | 7.2 GB |
| 35000 kbit/s | 262.5 MB | 15.75 GB |
How to use the video bitrate calculator
Choose what you want to find
Pick “File size” to find how big a recording will be, or “Bitrate for a size limit” to find the video bitrate that keeps a file under a limit, such as the 25 MB attachment limit of an email service.
Enter the bitrates and the length
Type the video and audio bitrates in kbit/s and the length as seconds, minutes:seconds or hours:minutes:seconds. Leave the audio field empty for a video without sound.
Read the result
The size appears in MB and in GB and GiB, next to the combined bitrate. In the limit mode you get the video bitrate to set in your encoder, and the total including the audio.
How file size follows from bitrate
A bitrate is the amount of data used for each second of recording. File size is the combined bitrate times the length, divided by 8 to turn bits into bytes. In this calculator one kilobit is 1000 bits, as in network and video specifications. For a 10-minute video at 5000 + 128 kbit/s that is 5128 × 1000 × 600 ÷ 8 = 384600000 bytes, or 384.6 MB.
To fit a size limit the same formula runs backwards: the total bitrate is the size in bits divided by the length, and the video bitrate is what remains after the audio. A 25 MB limit over 3 minutes with 128 kbit/s audio leaves 983.1 kbit/s for the picture. The result is the payload only. The file container (MP4, MKV and others) adds headers and an index, so the finished file is somewhat larger, and a variable-bitrate encoder only averages the target. Aim a few percent below the limit.
Video bitrate questions
How do I calculate video file size from bitrate?
Add the video and audio bitrates in kbit/s, multiply by 1000 to get bits per second, multiply by the length in seconds and divide by 8. At 5000 + 128 kbit/s for 600 seconds that gives 384600000 bytes, about 384.6 MB.
What video bitrate fits a 25 MB limit?
It depends on the length. For 3 minutes with 128 kbit/s audio, 25 MB allows about 983 kbit/s of video, and a 1-minute clip allows about 3205 kbit/s. Enter your own length in the limit mode, and note that MB here means 1000000 bytes. Some services count 25 MiB, which is 4.9% more.
Why is my exported file bigger than the calculated size?
The calculator counts the video and audio data. The container adds its own headers and index, and an encoder using variable bitrate only averages the figure you set, so the file can land above or below it. Keep a small margin under a hard limit.
What is the difference between kbit/s and kB/s?
Bitrates are written in kilobits per second (kbit/s). A kilobyte is 8 kilobits, so 5000 kbit/s is 625 kB/s. Always check which unit an encoder or a service asks for, because the same number differs by a factor of 8.
How much space does one hour of video use?
At 1000 kbit/s one hour is 450 MB, at 5000 kbit/s it is 2.25 GB and at 16000 kbit/s it is 7.2 GB, before audio. The table on this page lists more bitrates per minute and per hour.
Does this calculator read my video file or send anything anywhere?
No. It only does arithmetic on the numbers you type, in your browser tab. It never opens a video, so it cannot measure the bitrate of an existing file.