Drop a batch of audio or video files, or a whole folder, to read every file's length on your device and add them up. See the total runtime, average and longest file, the start time of each file, how long it takes at faster playback speeds, and export the list as CSV.
Last updated:
Drop audio or video files here
MP4, MOV, WebM, MKV, MP3, M4A, WAV, OGG, FLAC… · many at once · read on your device, nothing is uploaded
Showing 3 generated sample clips. Add your own files to replace them.
Total runtime0:000 seconds
Files counted0
Average length–
Longest / shortest–
Files and their durations
#
File
Duration
Starts at
Size
Remove
No files yet. Drop some audio or video files above.
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How to use the Media Duration Calculator
Drop your files into the box, or click Choose files or Choose folder. Three generated sample clips are shown until you add your own.
Wait a moment while each file's length is read from its metadata; files that can't be read are flagged and left out of the total.
Sort the list by name, duration, size or type, and remove any file you don't want counted.
Set a gap between files or a daily viewing time to see total runtime with pauses and how many days it takes.
Download CSV for a spreadsheet, or copy the timestamp list or the total runtime.
How the total runtime is worked out
Every audio and video container stores its own length. MP4 and MOV files keep it in the mvhd header as a duration count and a timescale (duration ÷ timescale = seconds), WAV files store the audio data size and the byte rate (data size ÷ byte rate = seconds), and formats such as WebM, MKV, MP3, OGG and FLAC are read by your browser's built-in media engine. The tool reads only this metadata, never the whole file, so it is fast even for very large videos.
Total runtime = sum of all readable file durations + gap × (number of files − 1).
Start time of a file = sum of the durations (and gaps) of every file before it in the current sort order.
Time at a faster speed = total runtime ÷ speed. 7 h 30 min of lectures at 1.5× = 450 min ÷ 1.5 = 5 h.
Days to finish = total minutes ÷ minutes per day, rounded up. 450 min at 30 min/day = 15 days.
Total time at common playback speeds
Total runtime
1.25×
1.5×
1.75×
2×
1:00:00
0:48:00
0:40:00
0:34:17
0:30:00
2:30:00
2:00:00
1:40:00
1:25:43
1:15:00
5:00:00
4:00:00
3:20:00
2:51:26
2:30:00
10:00:00
8:00:00
6:40:00
5:42:51
5:00:00
24:00:00
19:12:00
16:00:00
13:42:51
12:00:00
Tips for accurate totals
Name files with numbers (Lesson 1, Lesson 2 … Lesson 10). The Name (natural) sort keeps 10 after 9 instead of after 1, so start times match the intended order.
Use the gap setting for anything played back to back: a few seconds for autoplay between videos, or 2 seconds between tracks on a typical audio CD.
Check unreadable files: AVI, WMV and some MKV files use codecs that not every browser supports. Try a different browser, or convert the file to MP4 first, then add it again.
Audio CD and disc limits: a standard audio CD holds about 74 to 80 minutes, a C90 cassette 45 minutes per side, and a 12-inch LP roughly 18 to 22 minutes per side, so compare your total before burning or pressing.
Need to add times typed by hand? For a list of lengths you already know (like 3:45, 4:12), a playlist or time duration calculator is quicker than collecting the files.
Frequently asked questions
How do I find the total length of many video files?
Drop all the files (or the folder that holds them) into the box above. The tool reads each file's duration from its metadata and adds them together, showing the total in hours, minutes and seconds along with a per-file list.
Are my files uploaded anywhere?
No. Durations are read by your own browser using its built-in media player and, when needed, by reading a few header bytes of the file. Nothing leaves your device, so large or private files are fine and the tool keeps working offline once the page has loaded.
Why does a file show 'Can't read duration'?
Your browser could not open the file's metadata, usually because the codec or container isn't supported (for example some AVI, WMV or older MKV files) or because the file is damaged or incomplete. MP4, MOV and WAV headers are also read directly, so those often work even when the browser can't play them. Unreadable files are excluded from the total.
How accurate are the durations?
They come from the container's own duration field, which is normally accurate to a few milliseconds. Variable bitrate MP3 files without a header index can be off by a second or two in some browsers. The total is the exact sum of the listed durations, plus any gap you add.
How is the time at 1.5× or 2× speed calculated?
Playback time at a faster speed is the total runtime divided by the speed. For example, 6 hours of lectures at 1.5× takes 6 ÷ 1.5 = 4 hours, and at 2× it takes 3 hours.
What does the gap between files do?
It adds a fixed pause after each file except the last, like the countdown between autoplay videos or the 2-second pause between tracks on many audio CDs. The start and end times in the list include these gaps.
Is there a limit on the number or size of files?
There is no fixed limit. The browser only reads metadata, not the whole file, so even multi-gigabyte videos are fast. Hundreds of files work fine; they are read a few at a time to keep the page responsive.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.