Reference: Crowd Density

Crowd density is the multiplier that relates participant turnout and square footage.

It’s routine for organizers to overestimate crowd sizes. There’s no upside in publicly arguing about turnout, but it’s useful for the teams responsible for managing logistics to have a realistic understanding of the numbers involved.

Rallies

A busy rally or crowd waiting to begin marching is often around five square feet per person (or two people per square meter).

The densest portions of a rally crowd can be as much as twice as crowded, approaching two and a half square feet per person (or four people per square meter), comparable to the front row of a concert — but this is not common, and generally only applies in a small area closest to the speaker’s podium or other center of attention. The outer edge of the crowd often trails off into a loose penumbra that is much less dense, and when you average those areas together, the overall density will rarely be much tighter than four or five square feet per person.

Marches

A dynamic protest march or informal parade is often around ten square feet per person (or one person per square meter).

A march that is moving faster will typically be spread out more, or have gaps between clusters or contingents, resulting in overall densities closer to twenty square feet per person (or two square meters per person, equivalent to half a person per square meter).

Estimating Crowd Size By City Blocks

For marches in Manhattan, you can take advantage of the standard size of city blocks to make quick estimates as follows:

• A city block between numbered streets averages 264 feet (260 feet for standard side-streets, alternating with 300 feet for the occasional larger cross street) — when making quick estimates I round this off to 250 feet.
• When marching in the street, traffic lanes are generally about 10 feet wide (varying between 10–12 feet, but I round down because people generally don’t use the edges closest to the curb).
• A traditional midtown avenue typically has four travel lanes (although note that many avenues are now narrower than this, thanks to bike lanes and traffic-calming measures).
• If our crowd is marching, it’s likely about ten square feet per person, divided by ten a foot lane, or about one marcher per linear foot per lane — giving us approximately 250 people per lane per block, or 1,000 people per block for a four-lane avenue.
• If the crowd is stationary and packed in — for example, if folks are lining up behind the front banners in preparation for marching — the crowd is likely twice as dense, suggesting 2,000 people per block for a four-lane avenue.

Reference Scale