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 up on observing Khufu’s failing health during the later years. So we many 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 pyramid with the formula: 1/3 x Bh (where B is the area of base and h is 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 workman 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 been able to bear the weight. A safe and easy way of doing this was to convert slabs into component of 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 less chances of 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 main 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 1,00,000 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 workmen 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 floors” might have required lesser number of workmen.

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% laborers were needed for quarrying and transportation and 50% for laying the slabs. When construction reached the peak, the ratio undergoes a drastic change. Fewer slabs were needed but still around 72% laborers were engaged in the challenging job of transporting the stones to the top. The laborers laying the slabs were not more than 28% of the total labor force. The point to be noted is that the number of laborers 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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