Video Length Calculator
Length (s) = file size (bits) ÷ total bitrate (bits/s). Enter a file size and bitrate to get the running time, paste clip durations to get the total, or convert frames to timecode at any frame rate.
Use the Video Length Calculator
How long is the video?
Formula
seconds = size (bytes) × 8 ÷ ((video kbps + audio kbps) × 1000) ÷ overhead
Variable-bitrate files use the average bitrate, which your player's media info or ffprobe reports.
Total length of several clips
One clip per line: 1:30, 00:02:15, 95 (seconds) or 00:00:10:12 (with frames). Names on the line are ignored.
Video Parameters
Cards are sold in decimal GB; the usable space after formatting is a little lower.
Duration Inputs
For adding and subtracting timecodes, use the timecode calculator.
The bar shows how much of each slot the current duration fills; a faded bar means it runs over.
Video length per GB at common bitrates
Minutes of video in 1 GB (109 bytes) and in a 64 GB card, with 2% MP4 overhead. Real recordings vary with the encoder and scene complexity.
| Format | Bitrate | MB per minute | Minutes per GB | 64 GB card |
|---|---|---|---|---|
| 720p30 H.264 (web) | 5 Mbps | 38.3 | 26.1 | 27 h 53 min |
| 1080p30 H.264 | 8 Mbps | 61.2 | 16.3 | 17 h 26 min |
| 1080p60 H.264 | 12 Mbps | 91.8 | 10.9 | 11 h 37 min |
| 4K30 H.265 (streaming) | 20 Mbps | 153.0 | 6.5 | 6 h 58 min |
| 4K30 H.264 (camera) | 50 Mbps | 382.5 | 2.6 | 2 h 47 min |
| 4K30 ProRes 422 HQ | 707 Mbps | 5,408.6 | 0.2 | 12 min |
Worked examples
- Length from size. A 1 GB MP4 with 8,000 kbps video and 192 kbps audio: 1,000,000,000 × 8 ÷ 8,192,000 = 976.6 s of stream; ÷ 1.02 overhead = 957.4 s, about 15 min 57 s.
- File size from length. 10 minutes at 8,000 kbps total: 8,000,000 ÷ 8 × 600 = 600 MB of data, 612 MB with 2% overhead.
- Adding clips. At 25 fps, 00:00:10:12 + 1:30 + 00:02:00:00 = 262 + 2,250 + 3,000 = 5,512 frames = 00:03:40:12, or 220.48 s.
- 29.97 fps drift. One real hour is 107,892 frames. Non-drop timecode reads 00:59:56:12, drop-frame reads 01:00:00;00.
Summary
Four tools share one page. Length from file size divides the file's bits by the combined video and audio bitrate and removes container overhead. Add clips sums durations given as HH:MM:SS, MM:SS or SMPTE timecode with frames. The file size estimator runs the same formula forward, and the duration converter moves between real time, frame count and timecode, with drop-frame timecode for 29.97 and 59.94 fps. Sizes use decimal units (1 GB = 1,000,000,000 bytes) as cameras and memory cards do; the binary GiB figure that Windows shows is listed next to it.
How it works
- Choose a tab: Length from File Size, Add Clips, File Size Estimator or Duration Converter.
- Length from file size: enter the size, the video bitrate and the audio bitrate. Duration = size × 8 ÷ bitrate ÷ container overhead.
- Add clips: paste one duration per line (1:30, 00:02:15 or 00:00:10:12 with frames) and pick the frame rate; the total is shown as real time and timecode.
- File size: enter the duration and total bitrate to get the size in MB/GB and how many clips fit on common memory cards.
- Duration converter: change hours/minutes/seconds, total seconds or frame count and the rest update, including non-drop and drop-frame timecode.
Use cases
- Work out how long a downloaded or recorded file runs when only the size and bitrate are known.
- Total the running time of several clips for an edit, a playlist or a course.
- Check whether a finished video will fit within an upload size limit.
- Calculate how many minutes of footage fit on a memory card at a given recording bitrate.
- Convert a frame number from an NLE timeline into SMPTE timecode for subtitle sync.
- See why one hour of 29.97 fps non-drop timecode is 3.6 seconds longer than one real hour.