Video File Size Calculator

What to work out

Video bitrate, Mbps

Audio bitrate, kbps

Duration, minutes

Result

File size, MB1,889.4
Video bitrate, Mbps25
In GB1.845
Per minute, MB188.94
Total bitrate, Mbps25.19
Audio share, %0.8%
Assessment—

Bitrate times time

Works out video file size from bitrate and running time, and the reverse — the bitrate needed to fit a given file size.

Video size is set neither by resolution nor by duration on their own but by bitrate — data per second. Eight megabits a second for a minute gives sixty megabytes whether the footage is 1080p or 4K.

The one catch is the division by eight: bitrate is measured in bits and file size in bytes. Then there is audio, which next to video barely registers — 192 kilobits against 25 megabits is under one percent of the file.

What this calculator shows

File size in megabytes and gigabytes, and the weight of one minute
The reverse: the bitrate that fits a target file size
The share of the file taken by audio

What to keep in mind

The calculation is for constant bitrate. Variable bitrate typically comes out 10 to 20 percent smaller.
Rough guides: 8 to 12 Mbps for 1080p, 35 to 45 for 4K, 100 and up for shooting in an editable format.

FAQs

How big is an hour of video?

At 8 Mbps about 3.6 GB, at 25 Mbps roughly 11.3 GB, and at 100 Mbps around 45 GB.

What bitrate does 1080p need?

8 to 12 Mbps is fine for viewing; recording for an edit uses 50 and up so that colour grading does not fall apart.

How do I fit a video into a size limit?

Divide the target megabytes by the running time in seconds and multiply by eight — that gives the total bitrate in megabits you can afford.

Does resolution affect file size?

Only indirectly. Bitrate sets the size, but 4K at a low bitrate looks worse than 1080p at the same one — which is why higher resolutions get higher bitrates.

Worked example

Ten minutes of 4K

Input: 25 Mbps video, 192 kbps audio, 10 minutes

Output: 1,889 MB, which is 1.85 GB

Note: Almost two gigabytes for ten minutes. Audio takes under one percent of that — economising on it is pointless, and the difference is audible immediately.

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Video File Size Calculator

Result

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