The first conjecture about the number of workers engaged in building Khufu’s pyramid has been given by the Greek scholar Herodotus. He said that about 100,000 workmen had toiled to build Khufu’s pyramid around 2500 BC.

Herodotus was a historian and not an engineer, but his estimate was not questioned – not without reason. If the Taj Mahal, which is considerably small in size when compared to the pyramid, required 22,000 workers to build it in 22 years, the pyramid could have easily needed 100,000 men.

However, this estimate appears to have been greatly exaggerated. The latest estimate mentions 12,000 only, while the findings of the Denver Museum of Natural History claim that in the beginning 12,800 would have been required and towards the completion of construction 621 could have been more than sufficient!

How can we believe that only so many workmen built such a colossal structure? There is no accurate information regarding this in contemporary records, so we have to work it out for ourselves. For this, we must assume certain things.

The first important assumption is regarding the time factor. How many years did it take to build the pyramid? King Khufu had started work on the pyramid immediately after ascending the throne. He ruled for 23 years before his death. It is highly likely that Khufu’s courtiers were continuously monitoring the work and speeded it upon observing Khufu’s failing health during the later years. So we may assume that at the time of the king’s death, the pyramid was almost ready. The construction, therefore, must have taken 8,400 days. We may also assume that the workmen worked on all the days of the week.

After having estimated the time taken for construction, we now have to count how much energy was spent in building the great pyramid. The pyramid is 146.7 meters (481 feet) high, and its base is a square with each side 230.4 meters (756 feet) long. We can calculate the volume of the pyramid with the formula: 1/3 x Bh (where B is the area of the base and h is the height).

The volume would thus work out to 1/3 x 230.4 x 230.4 x 146.7 = approx. 2.6 million cubic meters.

However, from the point of view of the workmen and also to have an idea of the amount of effort put in, it may be more relevant to consider weight rather than volume. Mainly limestone has been used in Khufu’s Pyramid – almost 2.3 million slabs. The weight of limestone is, on an average, 2,700 kg per cubic meter. So, the total mass of material used works out to 2700 x 2.6 million = 7 billion kilograms.

It would require 25,20,000 million Joules of energy to construct this pyramid from the base to the peak (Joule is a unit to measure energy or work, like calorie). A healthy worker can give output equivalent to 2,40,000 Joules per day. So, about 1,250 workmen should be able to construct Khufu’s Pyramid in 8,400 days.

The quarries supplying limestone were at some distance. Slabs of an average of 2.5 tons would be cut from the quarries to be transported to the construction site by a different group of workmen. How did they transport the slabs?

A cart with wheels would not be able to bear the weight. A safe and secure way of doing this was to convert slabs into a component of a wheel. Such a wheel would be much broader than the wheel of a cart, and the weight would be evenly distributed, so there would be fewer chances of a breakdown. However, this discovery was made nearly 2,400 years after the age of the pyramids. The stones for Khufu’s pyramid were probably shifted on round, long and thick wood logs. (Ancient Egyptian wall carvings also show that this was the practice).

In the limestone quarries, boulders had to be hewed into smaller pieces, finished into slabs, and dragged along the place of construction. The founder and chief mathematician of Denver Museum of Natural History, Stuart K. Wyre calculated that 14 laborers per cubic meter of slabs would be needed for dragging them to the construction site.

Since Khufu’s pyramid was built in 8,400 days, we assume that 310 cubic meters of slabs were fixed daily. The quarry and transporting laborers would then have been 14 x 310 = 4340. Add 1,250 laborers needed for construction to this figure and the final tally comes to 5,590 laborers.

Surprised? Herodotus estimated the number as 100,000, and this number was generally accepted. On the other hand, the new estimate of 5,590 is barely 6% of that! Consider this as an average figure. The great pyramid of Egypt took 8,400 days to build, and it is not likely that the number of workers remained the same throughout. The base of the pyramid covered much more area than the rest of the structure. So a large number of laborers must have worked on the “ground floor”. After that, the structure gets narrower, and the “upper levels” might have required a lesser number of workmen.

The final estimate is that in the beginning, there were 12,800 workmen, and at the top of the pyramid, the number reduces to 621. This is because the narrow peak would not require too many slabs. Moreover, there was not enough space for many people to work there.

Another thing we learn from the chart is that during the construction of the base, 50% of laborers were needed for quarrying and transportation and another 50% for laying the slabs. When construction reached its peak, the ratio undergoes a drastic change. Fewer slabs were required, but still, around 72% of laborers were engaged in the challenging job of transporting the stones to the top. The workers laying the slabs were not more than 28% of the total labor force. The point to be noted is that the number of workers varied at different stages of construction but the average figure was less than 10,000!

More reading:

Great Pyramid of Giza (Wikipedia)

Wonders of the World (Wikipedia)

Egyptian pyramid construction techniques (Wikipedia)

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