So just how do you count the crowds that turned out for the biggest uprising in history?

The Egyptians reckon 30 million people were on the streets in recent anti-Islamic Brotherhood demonstrations.

But counting 30 million people is an impossible task – and what if some were counted more than once?

Certainly, the numbers hitting the streets and squares of Cairo and other major cities were big.

Tahrir Square was the centre of the protest – and the supporters of the protests claim millions crammed in to the space.

## The number’s up

But it’s obvious from looking at the size of the square that the maximum capacity is nearer 500,000 and that would be at a massive squeeze.

In fact, 30 million people is about 45% of the nation’s population – and considering official figures show 20% of the population are children under 10 years old and at least the same number would be too old or inform to turn out, the figure looks less and less plausible.

Every able-bodied adult Egyptian would have had to join the protest to hit the numbers the protestors claim.

A government spokesman suggested the figure was nearer 14 million, while the opposition reckoned the real total was a lot less than that.

All sides have something to prove by inflating demonstration figures.

The pros want to show they have popular support, the antis want the opposite and the government have their own agenda.

So how do the experts try to put a headcount on demonstrations and turn outs like Royal weddings and Papal visits?

## Counting rules

Well, there are no hard and fast rules.

One way is to take an aerial picture of an area with defined boundaries, like Tahrir Square.

Mathematicians then put a grid on the image and blow up one of the squares and simply count the heads and multiple the number by the total number of squares in the grid.

That gives crowd density, but does not account for people moving about.

Another method is to count the number of people moving past a specific point on a demonstration route, but this does not include people who joined the demo after that point or left before reaching the counter.

So in the end, unless the event is ticketed with entry control, no one really knows how big a crowd is – it’s all down to whether you are for or against the demonstration and some inspired guesswork.