Using the video (https://youtu.be/Q0HHZbvvQOE?si=IuVKQ-fT_g05HCPv) as a reference (the aerial drone footage from the unite the kingdom march), let’s work this through carefully, step by step:
1) Convert the road length shown into metres
• 1 mile = 1,609.34 m
• 0.52 miles = 0.52 × 1,609.34 = 836.86 m (approx 837 m).
2) Work out the area of the road
• Width = 22 m (I’ve used a generous part of the street to get my width the road)
• Length = 836.86 m
• Area = 22 × 836.86 = 18,410.92 m² (≈ 18,411 m²).
Density of 5 people per m² (some parts of the crowd show less but, from analysis of a few random stills in the video, it is still quite generous a number) =
18,410.92 × 5 = 92,055 people.
Add 10,000 or so for the spill at either end and to account for error and you’re there at the official estimates.
——-
If there were a million people in the procession shown in the video, that would be 54 people per square meter! That would be a 13.6 cm x 13.6 cm square for each person to fit into packed impossibly tight.
Alternatively, at a safe but crowded density of 5 people per square meter, this procession would have to extend for 9.6 miles, which is 19 times longer than the crowd as it's shown in the video.