How Many Workers Did It Take to Build the Great Pyramid of Giza?

The Great Pyramid of Giza was built around 2600 BC and was the tallest building in the world for almost 4000 years. It contains approximately 2.3 million blocks weighing in the order of 6-7 million tons. How many people did it take to build the Great Tower? Vaclav Smil in Numbers Don’t Lie offers an interesting calculation method:

The energy of the Great Pyramid (required to lift the weight above the ground level) is about 2.4 billion joules. Calculating this is very simple: it is simply the product of the acceleration due to gravity, the weight of the pyramid, and the center of mass (fourth of its height)…I take an average of 2.6 tons per cubic meter so the total weight is about 6.75 million tons.

Humans are able to convert about 20 percent of food energy into useful work, and in active men it is up to 440 calories per day. Therefore, lifting stones would require about 5.5 million (2.4 trillion/44000) man-days, or about 275,000 days per year [a] 20 years, and about 900 people can deliver that by working 10 hours a day 300 days a year. The same number would be needed to pile stones on a rising structure and smooth the layers of stone…And to cut 2.6 million cubic meters of stone in 20 years, the project would require about 1,500 masons working 300 days a year and producing 0.25 cubic meters of stone per person…the total number will be about 3,300 workers. Even if we could repeat that to be able to account for designers, editors and illustrators etc. etc….the total number will still be less than 7,000 workers.

…At the time of the construction of the pyramid, the total population of Egypt was 1.5-1.6 million, so an invested force of less than 10,000 would not have achieved any significant impact on the country’s economy.

I was surprised at the low number and amused by the unusual way of counting. Archaeological evidence from a nearby labor site suggests 4,000-5,000 local workers, not including carpenters, porters and designers and support workers. So, Smil’s calculation looks very good.

What other unusual figures do you know?