Get YouTube Playlist Length/Duration. It not only shows the playlist duration but also show several other important metrics like the number of the channels in that playlist, view count, channels having the highest/lowest video in the playlist and many more promising metrics. * Click on the extension. Enter the Playlist ID or URL in the input field and click on Calculate Playlist Length. * Go to any Playlist on YouTube. You will see a button Calculate Playlist Length, click on it.