What is Bitrate?
Definition
Bitrate is the amount of data used to represent one second of video or audio, measured in kbps or Mbps. It is the main factor controlling both file size and quality - higher bitrate means a larger file and usually better quality.
Bitrate counts how many bits of data are spent on each second of media. Video bitrate is usually given in megabits per second (Mbps) and audio in kilobits per second (kbps). Because data accumulates over time, file size is roughly bitrate multiplied by duration, so a 10 Mbps clip uses about 75 MB per minute no matter its resolution.
For a given codec, bitrate is the strongest lever over picture and sound quality. Too low a bitrate causes blocky compression artifacts, banding, or muddy audio; too high wastes space and bandwidth with no visible benefit. Encoders use either constant bitrate (CBR), which holds a fixed rate, or variable bitrate (VBR), which spends more bits on complex scenes and fewer on simple ones.
Bitrate is often confused with resolution. A 4K video at a low bitrate can look worse than a well-encoded 1080p file, because resolution sets the pixel grid while bitrate decides how much detail survives compression. The codec matters too: newer codecs like H.265 or AV1 reach similar quality at a lower bitrate than older H.264.
Quick facts
- Measured in kbps (kilobits per second) or Mbps (megabits per second)
- File size is roughly bitrate multiplied by duration
- Higher bitrate generally means a bigger file and better quality
- Typical 1080p H.264 video runs about 6-12 Mbps; MP3 audio 128-320 kbps
- CBR holds a fixed rate; VBR varies it by scene complexity