How this calculator works
The calculator removes the reserved portion of the drive, converts the usable bytes to bits, and divides by the combined audio and video bitrate.
The formula
usable storage bytes × 8 ÷ (video bitrate + audio bitrate)Bitrates are normalized to bits per second, durations to seconds, and storage to bytes before calculation.
Worked examples
- A 128 GB card at 25 Mbps video + 128 Kbps audio holds about 10.8 hours with 5% reserved.
- A 256 GB drive at 50 Mbps video + 320 Kbps audio holds about 10.7 hours with 5% reserved.
- A 1 TB drive at 100 Mbps video + 256 Kbps audio holds about 21.1 hours with 5% reserved.
Frequently asked questions
Can resolution tell me recording time?
Not by itself. Resolution and frame rate do not determine file size; the encoder and actual bitrate matter.
Why reserve storage?
A camera or drive may use some capacity for formatting, other files, or a safety margin. Change the reserve value to match your setup.