Works out a video file size from its bit rate and length: the bit rate is the data per second, so size is simply rate times time. It also shows how many hours fit in a given amount of free space.
This tool works out the size of a video file from its bit rate and its length. Use it to check that a card will hold a shoot, or to choose an export setting.
Here is the bit rate in Mbps, the length in minutes and the size in gigabytes. The bit rate is data per second, so multiplying by the seconds gives the total directly, and dividing by 8000 turns megabits into gigabytes.
Size follows from the bit rate alone. Footage in 4K becomes small at a low bit rate, and high definition becomes large at a high one. Higher resolutions take more space only because they need a higher bit rate to look right.
An hour of video at 8 Mbps comes to 3.6 GB. A card with 128 GB free would hold about 35.6 hours of it.
8 Mbps × 3600 seconds is 28800 megabits. Dividing by eight gives 3600 MB, or 3.6 GB.
Audio is not included. A soundtrack runs at perhaps 128 to 320 kbps, slight beside the picture but noticeable over long recordings.
With variable bit rate encoding the real size moves up and down with the content. The figure here is an average estimate.