Why do videos of the same length have different file sizes?
Understand how bitrate, resolution, frame rate and compression affect the space a video needs.
Duration is only one part of file size
Two videos can both be five minutes long and still take up very different amounts of storage. One might contain a mostly still presentation, while the other contains detailed scenes and fast movement.
The amount of data stored each second is called bitrate. For a given duration, a higher average total bitrate generally produces a larger file. Total bitrate includes both video and audio.
A simple size estimate
For a rough estimate, multiply the total bitrate in megabits per second by the duration in seconds, then divide by eight. The result is approximately the size in decimal megabytes, before small container overheads.
For example, a 60-second video with a total average bitrate of 8 megabits per second is approximately 60 MB. This is an estimate rather than a promise about the size of a particular download.
Resolution does not tell the whole story
Resolution describes the dimensions of the video frame. A higher-resolution video can contain more detail, but its final size also depends on bitrate and compression.
A heavily compressed 1080p video can be smaller than a less compressed 720p video. Do not judge file size or picture quality from the resolution label alone.
Movement, frame rate and compression matter
Fast movement, fine textures and visual noise can need more data to preserve clearly. A higher frame rate also means more frames per second, although encoding settings determine how much the size changes.
Different codecs can represent similar-looking video with different amounts of data. That efficiency can come with different playback compatibility or processing requirements.
What this means for your download
A short video can exceed a file-size limit, and a longer video can remain below it. Check the actual file size when it is available rather than estimating from duration alone.
All video saver currently limits social-video final files to 500 MB and applies a duration filter of up to 10 minutes. These are separate limits; satisfying one does not guarantee the other.