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No matter the turnout on Friday, it's a safe bet that Donald Trump will point out the "yuge" and "tremendous" size of the inauguration crowd.

But estimating just how many bodies there are in a sea of people is a delicate balance of rules of thumb, some basic math, and if we're lucky, getting an aerial view of the crowds.

A crowd gathers for President Obama's second-term inauguration, on January 21, 2013. Mladen Antonov / AFP - Getty Images

Steve Doig, a professor of journalism at Arizona State University's Walter Cronkite School of Journalism and Mass Communication, who has experience providing independent crowd estimates, said there's a reason why we'll likely hear some wildly varied crowd estimates on Friday.

"It's going to be treated as fake news between the two warring camps," he said, noting that Trump may think the estimates are too low, while "Never Trump" protesters might say it's too high.

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Crowd counting is never going to be 100 percent accurate, unless people are physically being counted going through a turnstile. However, there are some generally accepted rules of thumb, credited to Herbert Jacobs, who was a journalism professor at the University of California, Berkeley in the 1960s.

"It's basically a matter of knowing the area in square feet or meters," Doig told NBC News. "And then coming up with a reasonable density factor, which would be the average number of square feet each person is taking up. That factor is based on how closely together people are."

One way to check on square footage is to try Google Earth.

How Crowded Is that Crowd?

There are a few general rules of thumb when it comes to determining a crowd's density.

A "loose crowd" is one where everyone is about an arm's length from each other. In this case, the crowd estimate would account for 10 square feet per person.

That may sound like a lot, but it's only slight more than 3-feet by 3-feet per person. A crowd where people are grouped "shoulder to shoulder," would account for around 4.5 square feet per person.

If people are like sardines in a mosh pit, that's a density of about 2.5 square feet per person.

Of course, it's sometimes hard to grasp the true density of a crowd unless there's an overhead view. Some companies use drones to get a look at the crowd before providing a professional estimate.

However, inauguration attendees are being warned to leave their unmanned aerial vehicles at home, meaning a drone's eye view of the event is out of the question.