What is a b-roll coverage ratio?

The coverage ratio is the percentage of your finished video that will show b-roll footage instead of the talking head or main subject. A ratio of 70% means 70% of the final video plays b-roll over voiceover or interview audio.

What average clip length should I use?

Most documentary and corporate videos use 3–8 second b-roll clips. Shorter clips (2–4 s) feel more energetic; longer clips (6–10 s) feel more cinematic. If you are unsure, 5 seconds is a safe default.

Why add a safety buffer?

Not every clip you shoot will make the cut — some will be out of focus, too short, or redundant. A 20–30% buffer ensures you have enough usable footage. Experienced shooters often add 25% for run-and-gun work and 15% for controlled environments.

Does this account for multiple camera angles?

The result gives you the total unique b-roll seconds needed. If you plan to offer multiple angles of the same subject, multiply the clip count by the number of angles you want per scene.

Can I use this for social media short-form videos?

Yes. Enter the full duration of your reel or short (e.g., 0 min 60 sec) and set a high coverage ratio (80–100%) if you plan to run continuous b-roll with audio overlay throughout.

B-Roll Duration Planner

Enter your interview or voiceover duration, coverage ratio, and average clip length to get the exact number of b-roll clips and total shoot time you need.

Project Settings

Interview / Voiceover Duration

Minutes

Seconds

B-Roll Coverage Ratio: 70%

10% (minimal) 100% (full)

Average Clip Length (seconds)

Typical range: 3–8 seconds per clip.

Safety Buffer: 25%

0% (no buffer) 100%

Results

Fill in the settings and click Calculate.

Summary

This tool calculates how much b-roll footage to shoot for an interview or voiceover-driven video. Enter the audio duration, the desired coverage ratio, and the average clip length. The planner returns total b-roll seconds required, clip count with an optional safety buffer, and an estimated field shoot time. All math runs in your browser.

How it works

Enter the total duration of your interview or voiceover in minutes and seconds.
Set the b-roll coverage ratio — the percentage of your final video that will use b-roll over the talking head.
Enter the average length of each individual b-roll clip in seconds.
Add a safety buffer percentage to account for unusable or duplicate shots.
Read the results: total b-roll seconds needed, number of clips to shoot, and estimated shoot time.

Use cases

Pre-production planning for documentary or interview-style videos.
Calculating a shot list length before a b-roll filming day.
Budgeting shoot time when hiring a videographer by the hour.
Estimating how many location setups fit into a single shoot day.
Teaching video production students about coverage ratios.

Frequently Asked Questions

Last updated: 2026-06-19 · Reviewed by Nham Vu