Bitrate vs Resolution
Also known as: bitrate or resolution, video quality factors
Resolution is how many pixels a video frame contains, while bitrate is how many bits are stored per second of playback. File size is driven by bitrate and duration, not resolution alone, so a high-resolution clip recorded at a low bitrate can be smaller than a lower-resolution clip at a high bitrate.
- Video file size is approximately bitrate multiplied by clip duration.
- Resolution counts pixels per frame; bitrate counts bits stored per second.
- A high-resolution clip at low bitrate can be smaller than a low-resolution clip at high bitrate.
What each term means
Resolution counts the pixels in each frame, for example 1920x1080 for 1080p or 3840x2160 for 4K. More pixels can hold more detail but do not by themselves set the file size.
Bitrate is the amount of data stored per second, measured in megabits per second (Mbps). It reflects how much the encoder spends describing motion and detail. The storage size of a clip is roughly its bitrate multiplied by its duration, so a 20 Mbps clip uses about 2.5 MB per second.
Which one drives storage
Because size equals bitrate times duration, bitrate is the primary lever for file size. Raising resolution usually pushes recorders to use a higher bitrate, which is why 4K files are large, but the bitrate is what is actually being stored.
Frame rate compounds this: 60 fps at 4K typically needs a much higher bitrate than 30 fps to look smooth, so it produces bigger files at the same resolution. When cleaning up large videos, sorting by file size or bitrate finds the real space hogs faster than sorting by resolution.