How long should a YouTube documentary be?

The short answer

For most faceless documentary channels, 15 to 25 minutes is the sweet spot. It's long enough to tell a full story and to carry mid-roll ads, and short enough that a good share of viewers make it to the end. Many of the biggest documentary channels sit right in that range.

What length does for your channel

Videos of 8 minutes or more can carry mid-roll ads, which is why almost no documentary channel goes shorter. Past that point, a longer video adds more ad breaks and more watch time per viewer, and watch time is one of the signals YouTube uses to recommend videos.

But length only pays if people stay. A 30-minute video that loses half its audience in the first three minutes earns less, and gets recommended less, than a tight 15-minute one that holds them.

Length is only worth what viewers actually watch of it.

Match the length to the story

Different stories need different room:

• One event or one machine: 10 to 15 minutes. A single crash, a single engine, one famous test.
• One life, one company or one rivalry: 20 to 30 minutes. A rise and fall needs time for both halves.
• A whole era or a war: 40 minutes or more, or a series of parts. Split it where the story naturally turns.

If you find yourself padding to reach a length, the story is shorter than you planned. Cut, don't stretch.

Words for each length

Narration runs at about 150 words a minute. Use this as a starting point when you plan a script:

• 10 minutes: about 1,500 words
• 15 minutes: about 2,300 words
• 20 minutes: about 3,000 to 3,300 words
• 30 minutes: about 4,500 words

For how to make those words hold attention, see our guide on writing a documentary script people finish.

Retention beats length

Open the audience retention graph in YouTube Studio for every video you publish. The places where the line drops tell you what to fix next time: a slow opening, a chapter that ran long, a stretch where nothing new happened on screen. Fix those, and your videos can grow longer without losing people.

A good habit for a new channel is to start at 12 to 15 minutes, watch retention for a few uploads, and lengthen only once viewers are consistently staying past the halfway point.