Formula
Megabits per second become bytes over the length of the recording:
bytes = Mbps × seconds × 1,000,000 / 8
A gigabyte on this page is 1,000,000,000 bytes. One hour at 8 Mbps is 3.6 of those gigabytes. Download time is a different page because it also needs a connection speed.
Assumptions
- The bitrate is constant.
- Audio is included only if it is already inside the bitrate you enter.
- The container overhead is ignored.
Worked example
Video at 8 Mbps for 1 hour is about 3.6 GB.
Input definitions
- Bitrate
- Megabits per second for the finished file.
- Duration
- Hours, minutes, and seconds. At least one second is required.
Limitations
Variable bitrate, codecs, and audio tracks can move the real file away from this constant-rate estimate.
Questions
How do I find how long a drive will record?
That is this formula rearranged. Divide the free gigabytes by the size of one hour at your bitrate.
Is a gigabyte 1,024 megabytes here?
No. This page uses decimal bytes so they match megabits per second.