How Tall Is the Great Pyramid of Giza, and Has It Changed?

The numbers, and how sure they are

The pyramid was built for King Khufu, the first of the three kings who built at Giza, in the Fourth Dynasty. Its height when finished was about 146.6 metres, roughly the height of a 45-storey building. Each side of its square base measured about 230 metres; with the casing gone, the sides now measure about 227.

Some figures are measurements, others are estimates. The height and the base are measured. The number of blocks, often given as about 2.3 million with an average weight of about 2.5 tonnes, is a calculation from the volume, so treat it as an order of magnitude. The orientation, on the other hand, has been measured precisely: the sides face the four cardinal points with an error of only a few minutes of arc, a fraction of a degree.

What it looked like when it was new

The pyramid you see today is a stepped mountain of rough blocks. That is its core. When it was finished, the core was covered with a casing of fine white limestone, cut so precisely that the four faces were completely smooth. The casing stone came from the Tura quarries across the Nile, finer than the local stone of the plateau.

We even have a record of the work. In 2013 a French mission led by Pierre Tallet found papyri at Wadi al-Jarf, an ancient harbour on the Red Sea. Among them is the logbook of an official called Merer, who led a team of about 200 men. Dated to year 27 of Khufu’s reign, it records their trips carrying limestone from Tura to Giza by boat, when the casing was being fitted. The rest of the work is part of the bigger question of how the pyramids were built.

Where did the casing go?

It was reused. Fine, ready-cut limestone was too useful to leave on a tomb, and limestone was being taken from the Giza pyramids for buildings in Cairo by the twelfth century CE. Accounts also say a great earthquake in 1303 loosened many casing blocks, which made them easier to remove. By the nineteenth century almost all of the casing had gone, apart from a few blocks at the foot of the pyramid.

With the casing went the top of the pyramid, which is why the summit today is lower and blunt. So the pyramid has shrunk in two ways at once: it lost its smooth skin, which made the base slightly smaller, and its tip, which took away about eight metres of height. Its neighbour, Khafre’s pyramid, still keeps a cap of casing at the top and shows how all of them once looked.

The tallest building for about 3,800 years

For a very long time nothing built by people was taller. The record is usually said to have passed to Lincoln Cathedral in England, whose central spire, completed in 1311, reached about 160 metres; that makes about 3,800 years at the top for the pyramid. Some historians dispute the Lincoln claim, so the exact end date is debated. Lincoln’s spire did not last: it collapsed in a storm in 1548 and was never rebuilt, while the pyramid is still standing.

Is there still something hidden inside?

The inside of the pyramid is a system of passages and chambers, from the Grand Gallery to the King’s Chamber, explained in its own guide. In 2017 the ScanPyramids team announced in Nature that cosmic-ray imaging had revealed a large void above the Grand Gallery, at least 30 metres long. What it is remains open: some archaeologists, among them Zahi Hawass, argue that such gaps are simply part of the construction. The pyramid was the culmination of a century of experiments that began with the Step Pyramid of Djoser, and it still keeps some of its secrets.

Where to see it

The Great Pyramid stands on the Giza Plateau, on the western edge of Cairo. Casing stones are on show in the British Museum in London (EA 490) and in the National Museum of Scotland in Edinburgh.

Sources

• National Museums Scotland, “Pyramid casing stone”.
• PBS NOVA, “Pyramids: The Inside Story”.
• Big Think, on the logbook of Merer from Wadi al-Jarf (excavated 2013 by P. Tallet and G. Marouard).
• Morishima, K. et al., “Discovery of a big void in Khufu’s Pyramid by observation of cosmic-ray muons”, Nature 552 (2017).
• The Lincolnite and History Hit, on the Lincoln Cathedral spire (1311-1548).