Video Bitrate Calculator
Enter a file size and a duration to get the average bitrate of a video or audio file. You can also find how long a recording fits in a given size at a given bitrate.
How the bitrate is calculated
The bitrate is the amount of data used per second. From a size and a duration you can find the average bitrate.
- Bitrate (bit/s) = size (bytes) × 8 ÷ duration (seconds)
- Recording time (seconds) = size (bytes) × 8 ÷ bitrate (bit/s)
The × 8 is there because the size is in bytes and the bitrate is in bits (1 byte = 8 bits). The Video File Size Calculator does the opposite calculation: the size from a bitrate and a duration.
Mind the units
Bits and bytes, Mbps and MB/s, and GB and GiB are different things. Mixing them up can make the result wrong by a factor of 8 or by several percent.
| Pair | The difference |
|---|---|
| bit and byte | 1 byte = 8 bits. Bitrates and connection speeds are usually written in bits, and file sizes in bytes |
| Mbps and MB/s | Mbps is megabits per second and MB/s is megabytes per second. 1 MB/s = 8 Mbps |
| GB and GiB | 1 GB = 1,000,000,000 bytes (steps of 1,000) and 1 GiB = 1,073,741,824 bytes (steps of 1,024). A GiB is about 7.4% larger |
You can choose the size in bit, byte, KB to TB or KiB to TiB, and the bitrate in bps, kbps, Mbps, Gbps or MB/s. The result shows kbps, Mbps and MB/s side by side. In bitrates, k, M and G are steps of 1,000 (1 Mbps = 1,000,000 bit/s). To see how the size units differ, use the Data Size Converter.
Examples
- 2 hours of video in 4.7 GB: 4,700,000,000 × 8 ÷ 7,200 = about 5,222,222 bit/s (about 5.22 Mbps, about 0.65 MB/s)
- 10 hours in 128 GB: about 28.44 Mbps
- A video of 8.192 Mbps in total, saved to 128 GB: 125,000 seconds (34 h 43 min 20 s)
- The bitrate left for video: with 8.192 Mbps in total and 192 kbps for audio, 8.192 − 0.192 = 8 Mbps
Assumptions and notes
- The result is a theoretical average worked out from the size and the duration alone. The overhead of the container (the file format, such as MP4, that holds the video and audio together), subtitles and metadata are not included. In practice, leave some margin.
- For a video with a variable bitrate, the result is the average.
- The duration must be greater than 0 and at most 999 hours 59 minutes 59 seconds. The recording time is shown with the fraction of a second dropped.
- If you enter an audio bitrate, the bitrate left for video (the total minus the audio) is shown. If the audio is larger than the total, nothing is shown for video.
- The size and the bitrate can have decimals (up to 12 digits before the decimal point and 6 decimal places).
Source
The definition of the bit rate (bits conveyed per unit of time, with SI prefixes such as kilo = 1,000), the relation of 1 byte to 8 bits, and the formula size × 8 ÷ time follow Wikipedia, "Bit rate": https://en.wikipedia.org/wiki/Bit_rate (read on November 1, 2026; only the first part of that long page could be read word for word). The binary prefixes (kibi, mebi, gibi) follow Wikipedia, "Binary prefix": https://en.wikipedia.org/wiki/Binary_prefix (read on November 1, 2026; the same limit). They are explanatory articles, not standards.
Frequently asked questions
What bitrate do I need to fit a video in a given size?
Use "Bitrate from a size and a duration" with the size and the length of the video. Enter the audio bitrate too, to see what is left for video. In practice, go a little lower to allow for overhead.
Should I look at Mbps or MB/s?
Video bitrates are usually written in Mbps (bits). Download speeds are sometimes shown in MB/s (bytes). They differ by a factor of 8, so check the unit.
Why does the recording time come out longer than in practice?
Because overhead and variations in a variable bitrate are not included. Leave some margin.