How to Estimate the Crowd Size at a Public Gathering

In the aftermath of the recent inauguration of President Donald Trump, the media and the POTUS were at a disagreement as to the number of people who attended the event. The White House officials were proclaiming a larger number of attendees while most of the media objectively estimating lower numbers. So how do you determine crowd size? If it is a sporting event or a music concert, ticket sales will approximate the number of people in attendance. In the case of the inauguration or a protest or a rally, summing up the crowd with reasonable accuracy might seem impossible. Jacobs’ Method is a renowned technique employed by the media and the police (for security and emergency reasons) to estimate crowd size.

Herbert Jacobs formulated Jacobs’ Method in the 1960s. Jacobs, while working as a journalism professor at UC Berkley, observed Vietnam war protests frequently outside his office window. He noticed the area that the protesters stood on had a repeating grid-like pattern. By counting the number of people standing on a specific grid, he was able to extrapolate and estimate the number of protesters who would show up. Jacobs found that in the most densely packed crowds each person occupied about 2.5 square feet of space. This allocation of space is considered the maximum limit for a crowd without getting trampled, sometimes referred to as “mosh pit density.” Jacobs’ calculations accounted for different densities when sections of the grid space were filled by people taking up 4.5 square feet up to ten square feet. This simple method gave an excellent estimate of the number of protesters. Soon Jacobs’ Method became the standard protocol for crowd estimations.

Modern technology has made crowd size calculations using Jacobs’ Method easier. Software such as Google Earth can be used to delineate areas and partition grid sizes accurately. The omnipresent global media and social networking platforms are a source for finding video and photographs of almost any public gathering. Applying the Jacobs’ Method with this available information of grid sizes and crowd density is pretty straightforward. Most media broadcasts use this information to update crowd sizes live during an event. If the proper details can be gathered, anyone can calculate and estimate crowd sizes in real time.

In most instances, people are interested in an estimate of crowd sizes than an exact number. As such, compared to sophisticated image processing software with complicated algorithms, properly executed Jacobs’ Method fares well in estimating crowd sizes.

The discrepancies that appear in different reports on crowd sizes are due to the bias of the reporting organizations. A false claim on a higher number of attendees is usually to display popularity or to gain more supporters for a particular propaganda. Politics aside, Jacobs’ Method provides a practical way to estimate crowd sizes. Next time you are spinning records at a summer beach party, you can estimate the number of people dancing to your tunes.