I figured I needed to find out the area of that plaza before I could figure out how many people could fit into it. So I got the latitude and longitude coordinates of the roughly triangular plaza of the Thompson Center using Google Earth. I then calculated the area of the plaza at the Thompson Center using the Google Maps Area Calculator Tool. The highlighted area (click on the map to see it full size) where the rally took place constitutes 33,940.38 feet². Let’s be conservative (so to speak) and round it off to 30,000 square feet.
According to the Poynter Institute, working to improve American journalism since the 1970s, crowd estimates are difficult, but not impossible:
So by this rule of thumb, in 30,000 square feet of space a loose crowd would consist of about 3,000 people. A more tightly-packed crowd would contain more than 6,000 people, and a truly dense crowd, jam-packed into 30,000 square feet, could easily be close to 12,000 people.
A loose crowd, one where each person is an arm’s length from the body of his or her nearest neighbors, needs 10 square feet per person. A more tightly packed crowd fills 4.5 square feet per person. A truly scary mob of mosh-pit density would get about 2.5 square feet per person.
The trick, then, is to accurately measure the square feet in the total area occupied by the crowd and divide it by the appropriate figure, depending on assessment of crowd density.
Now this was a pretty tightly-packed crowd at yesterday’s rally, but it wasn’t 12,000 people. But I think my initial estimate of between 5,000 and 6,000 people is pretty close.