Pyramid Construction: How the Egyptians Built the Impossible

The pyramids of Egypt are the most massive stone buildings the world has ever seen. The Great Pyramid alone contains an estimated 2.3 million blocks, each weighing on average 2.5 tons, and the whole structure weighs 6 million tons. Yet it was built in less than twenty years, using only the tools and techniques available to a Bronze Age civilization. The story of how the Egyptians did it is the story of one of the great engineering achievements in human history.

For a closer look at specific questions (who built the pyramids, and how did they move the stone), see workers or slaves and moving massive stone blocks. For the historical context, see our guide to the Old Kingdom of Egypt.

Designing the Pyramid

Building a pyramid began long before the first stone was cut. The Egyptian engineers had to design the structure, choose the site, lay it out, and organize the supply of labor and materials. The chief architect was typically a high official of the royal court, often the Overseer of All the King’s Works (Egyptian jmj-rꜣ kꜣt nbty).

The basic design of a true pyramid is geometric. A square base, four triangular faces meeting at an apex, each face at a precise angle. To design a pyramid, the architect had to:

• Choose a square base of the right size.
• Set the angle of the faces (the “slope angle”), typically between 43° and 56°.
• Calculate the volume of stone needed.
• Design the internal chambers and corridors.
• Choose a site with solid bedrock.

The mathematics of the pyramid were remarkably sophisticated. The Egyptians had a precise value of pi (3.16, very close to the true value), and they used a system of proportions based on the seked, the reciprocal of the slope. The angles of the pyramids of Giza are close to 51°50’ (Khufu and Menkaure) to 53°10’ (Khafre), a slope chosen for reasons that are still debated, but which would have required sophisticated geometry to lay out.

Site Selection

The Egyptians chose their pyramid sites carefully. The most important factors were:

• Solid bedrock. A site with a single piece of bedrock, rather than fragmented or faulted stone, was essential to support the immense weight. The Giza plateau, Saqqara, and Dahshur were all chosen for this reason.
• Proximity to the Nile. Stone had to be moved from the river, and the site had to be accessible by boat. Giza, Saqqara, and Dahshur are all within a few kilometers of the flood plain.
• Proximity to the capital. During the Old Kingdom, the capital was at Memphis, and the major pyramids are all in the Memphis necropolis.
• A view of the rising sun. Egyptian religion held that the dead pharaoh would join the sun god Ra on his daily journey. Most pyramids are on the west bank of the Nile, looking east.

Laying Out the Site

Once the site was chosen, the architects laid out the pyramid with extraordinary precision. The four sides of the Great Pyramid are aligned to the cardinal directions with an error of less than 0.067 degrees, a precision that, in the twenty-first century, is still being studied by modern engineers.

How did the Egyptians achieve this? Modern scholars believe they used a combination of:

• Astronomical observation. The position of the sun and the stars at the solstice and equinox allowed the alignment of one side. The Great Pyramid, for example, is aligned almost exactly north.
• Plumb lines and sighting tools. The Egyptians used a plumb line and a level (a triangle with a plumb line hanging from the apex) to set the angles of the courses.
• Surveying. Egyptian surveyors could lay out a square of the size of the Great Pyramid’s base (about 230 meters, or 756 feet, on a side) to within a few centimeters of accuracy.

For a deeper look at the techniques, see our article on the Great Pyramid of Khufu and on the Old Kingdom of Egypt.

Quarrying the Stone

The stone for the pyramids came from three main sources:

• Local limestone. The core blocks of the Giza pyramids came from the plateau itself. The Egyptians cut the stone in quarries on the south side of the Giza plateau and on the west side of the Sphinx. Most of these blocks were relatively soft, low-quality limestone.
• Tura limestone. The fine white casing stones came from Tura, on the east bank of the Nile, about 12 km south of Giza. This limestone is of very high quality, and the casing stones gave the pyramids their smooth, brilliant white appearance in antiquity.
• Aswan granite. Granite, used for the inner chambers, the sarcophagi, and the lower courses of the Pyramid of Menkaure, came from Aswan, more than 800 km to the south.

Quarrying was done with copper tools, dolerite hammerstones, and wooden wedges. The Egyptians did not have iron tools until the very end of the Bronze Age, and most Old Kingdom quarrying was done with copper chisels and stone hammers. They cut channels into the rock with hand tools, hammered in wooden wedges, and then poured water on the wedges to expand them and split the rock. The result was stone blocks of the right size, ready to be moved.

Transporting the Stone

Once quarried, the stone had to be moved. The Egyptians used three main methods:

• Slipways and sledges. Most of the stone was moved on wooden sledges, dragged by teams of workers over slipways. In recent years, a team from the University of Amsterdam has shown that pouring water on the sand of the slipway reduced friction by 50%, allowing relatively small teams to drag enormous weights.
• Boats on the Nile. The Tura casing stones and the Aswan granite were moved by boat. The Egyptians built enormous barges (some of them more than 30 meters long) to carry the granite blocks downstream. Granite for the Great Pyramid’s inner chambers came more than 800 km from Aswan.
• Canals and harbors. Both Giza and Saqqara had artificial harbors, connected to the Nile by a system of canals. Recent work by the Ancient Egypt Research Associates (AERA) has revealed the layout of the Giza harbor system in some detail.

For more, see our article on moving massive stone blocks.

Building the Pyramid

Once at the site, the stones had to be raised to their final position. The Egyptians used ramps, of which there are several known types:

• Straight ramps running up one face of the pyramid. Long and easy to build, but the longer the pyramid got, the longer the ramp had to be.
• Zigzag ramps running up one or more faces in a series of switchbacks. The Egyptians may have used these at Giza, but the evidence is limited.
• Internal ramps, a hypothesis popularized by the French architect Jean-Pierre Houdin in 2007. The idea is that the ramp was inside the pyramid itself, spiraling up the inside as the pyramid was built.
• Comb ramps running up one face, with a steep section at the top for the final, most difficult blocks. This is one of the most commonly proposed solutions for the upper courses of the Great Pyramid.

The most recent archaeological work and the most detailed experimental reconstructions suggest that a combination of straight ramps and external ramps at different stages was used, depending on the height of the pyramid.

Setting the Casing Stones

The final step was the installation of the casing stones, the smooth, fine white limestone slabs that covered the outside of the pyramid. These were fitted with extraordinary precision: the joints between casing stones on the Great Pyramid are less than 1 millimeter (0.04 inches) wide.

The casing was applied from the top down, with the workers finishing each course before starting the next below. After the casing was complete, the pyramid was a perfect geometric shape, brilliant white in the sun. The casing was stripped during the medieval period to build the city of Cairo, but the precision of the casing stones and the way they were fitted has been the subject of intense study by modern engineers.

The Workforce

The pyramid builders were skilled Egyptian workers, organized by the state and paid in rations of bread, beer, and other staples. The AERA excavations at Heit el-Ghurab make it clear that they were not slaves. The Workers’ Village at Giza has shown that the workers and their families lived in well-built houses, and the Workers’ Cemetery shows that they were honored after death.

For more, see our article on workers or slaves and on who actually built the Great Pyramid.