A million-strong crowd sounds impressive, but how do the experts calculate that figure?

On Tuesday, the world watched as protesters took to the streets of Cairo, demanding the ousting of President Hosni Mubarak. It was dubbed the "million-man march", an estimate of just how many Egyptians had joined in the demonstration.

But where did the figure of one million come from? When such a crowd gathers, without tickets or being made to go through a turnstile, how do officials work out how many people were actually involved?

After huge protests against the Iraq war were organised in London in 2003, the estimates of how many people attended were almost as contentious as the war itself. While the police said that at least 750,000 people took part, organisers put the figure closer to two million. Is it possible ever to get an accurate figure?

The most common way to count a crowd is the Jacobs Method, named after its inventor, Herbert Jacobs. It was during his time as a journalism lecturer at the University of California, Berkeley during the 1960s anti-Vietnam war riots that he formulated his method. Having an office in a tower that overlooked the plaza where students gathered, Jacobs had a unique view and became frustrated with the police estimates, which he felt greatly exaggerated the number of people involved.

After getting hold of an enlarged aerial photograph of the mob scene, Jacobs divided it up into 1in squares and painstakingly counted all the heads using a magnifying glass. After four hours of counting, he worked out the figure to be less than half what police and newspapers had reported.

He then divided the plaza into 22ft squares and used this to find a more scientific way to calculate crowd size. He attended many of the rallies, and by counting the number of students in several of the squares and dividing accordingly, he was able to work out the average area occupied by an individual. He deduced that this varied from a minimum of 2.5 sq ft for a mosh pit-style mob crowd, to 4 sq ft for a tightly packed crowd, to 9.5 sq ft for a looser one. He then applied his formula to further rallies, checking it against photographs that he took himself.

While analysts still use this method, things have advanced since the Sixties and there are now all sorts of technologies used to assist with such estimations, including satellites, aerial photography, recorded video footage and surveillance balloons, which can be placed around an event's location and flown overhead.

The method is not without its flaws, and the simple answer is that it is impossible ever to know exactly how many people are in a crowd. But whether it's a demonstration, a royal wedding or a visit from the Pope, the reputations of organisations and personal egos can be ballooned or deflated by how large or small a crowd is reported to be.

Start your day with The Independent, sign up for daily news emails
election 2015The 10 best quotes of the campaign
A caravan being used as a polling station in Ford near Salisbury, during the 2010 election
election 2015The Independent's guide to get you through polling day
David Blunkett joins the Labour candidate for Redcar Anna Turley on a campaigning visit last month
voicesWhat I learnt from my years in government, by the former Home Secretary David Blunkett
Have you tried new the Independent Digital Edition apps?
ebooksA celebration of British elections
  • Get to the point
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Ashdown Group: Marketing Manager (B2B) - Romford - £40,000 + car

£35000 - £40000 per annum + car and benefits: Ashdown Group: Marketing Manager...

Ashdown Group: Helpdesk Analyst - Devon - £20,000

£18000 - £20000 per annum: Ashdown Group: Helpdesk Analyst - Devon - £20,000 ...

Ashdown Group: Data Scientist - London - £50,000 + bonus

£35000 - £50000 per annum + generous bonus: Ashdown Group: Business Analytics ...

Ashdown Group: IT Project Coordinator (Software Development) - Kingston

£45000 - £50000 per annum: Ashdown Group: IT Project Coordinator (Software Dev...

Day In a Page

General Election 2015: ‘We will not sit down with Nicola Sturgeon’, says Ed Balls

'We will not sit down with Nicola Sturgeon'

In an exclusive interview, Ed Balls says he won't negotiate his first Budget with SNP MPs - even if Labour need their votes to secure its passage
VE Day 70th anniversary: How ordinary Britons celebrated the end of war in Europe

How ordinary Britons celebrated VE Day

Our perception of VE Day usually involves crowds of giddy Britons casting off the shackles of war with gay abandon. The truth was more nuanced
They came in with William Caxton's printing press, but typefaces still matter in the digital age

Typefaces still matter in the digital age

A new typeface once took years to create, now thousands are available at the click of a drop-down menu. So why do most of us still rely on the old classics, asks Meg Carter?
Discovery of 'missing link' between the two main life-forms on Earth could explain evolution of animals, say scientists

'Missing link' between Earth's two life-forms found

New microbial species tells us something about our dark past, say scientists
The Pan Am Experience is a 'flight' back to the 1970s that never takes off - at least, not literally

Pan Am Experience: A 'flight' back to the 70s

Tim Walker checks in and checks out a four-hour journey with a difference
Humans aren't alone in indulging in politics - it's everywhere in the animal world

Humans aren't alone in indulging in politics

Voting, mutual back-scratching, coups and charismatic leaders - it's everywhere in the animal world
Crisp sales are in decline - but this tasty trivia might tempt back the turncoats

Crisp sales are in decline

As a nation we're filling up on popcorn and pitta chips and forsaking their potato-based predecessors
Ronald McDonald the muse? Why Banksy, Ron English and Keith Coventry are lovin' Maccy D's

Ronald McDonald the muse

A new wave of artists is taking inspiration from the fast food chain
13 best picnic blankets

13 best picnic blankets

Dine al fresco without the grass stains and damp bottoms with something from our pick of picnic rugs
Barcelona 3 Bayern Munich 0 player ratings: Lionel Messi scores twice - but does he score highest in our ratings?

Barcelona vs Bayern Munich player ratings

Lionel Messi scores twice - but does he score highest in our ratings?
Martin Guptill: Explosive New Zealand batsman who sets the range for Kiwis' big guns

Explosive batsman who sets the range for Kiwis' big guns

Martin Guptill has smashed early runs for Derbyshire and tells Richard Edwards to expect more from the 'freakish' Brendon McCullum and his buoyant team during their tour of England
General Election 2015: Ed Miliband's unlikely journey from hapless geek to heart-throb

Miliband's unlikely journey from hapless geek to heart-throb

He was meant to be Labour's biggest handicap - but has become almost an asset
General Election 2015: A guide to the smaller parties, from the the National Health Action Party to the Church of the Militant Elvis Party

On the margins

From Militant Elvis to Women's Equality: a guide to the underdogs standing in the election
Amr Darrag: Ex-Muslim Brotherhood minister in exile still believes Egypt's military regime can be replaced with 'moderate' Islamic rule

'This is the battle of young Egypt for the future of our country'

Ex-Muslim Brotherhood minister Amr Darrag still believes the opposition can rid Egypt of its military regime and replace it with 'moderate' Islamic rule, he tells Robert Fisk
Why patients must rely less on doctors: Improving our own health is the 'blockbuster drug of the century'

Why patients must rely less on doctors

Improving our own health is the 'blockbuster drug of the century'