When Were the Pyramids of Giza Built?

The usual answer is: around 2,560 BC. It appears in encyclopedias, on signs, and in every travel guide, and it is not wrong.

It is just something different than most readers assume. It is not a recorded date nor a measurement result. It is the outcome of a chain of deductions that rests on assumptions at several points, and this chain can be traced step by step.

This is not a relativization. In the end, a remarkably robust statement remains: the three great pyramids were created in the 26th century BC, within about eighty years, under three successive kings. This statement is supported by multiple independent methods and is not seriously disputed by research.

What cannot be stated with exact precision is the year itself. And the reason for this is so unexpected that it supports the rest of this page: The entire calculation hinges, among other things, on how often livestock was counted in ancient Egypt.

Egypt had no continuous year numbering

To understand how the date arises, one must take a detour. The ancient Egyptians did not have a continuous year numbering system like ours.

There was no era from which counting began, no year zero, no calendar that continued across dynasties. Dating was done according to the regnal year of the respective king: in the third year of Khufu, in the seventh year of Khafre. When a king died, counting started again at one.

This was practical for administration. For posterity, it is a problem, because such a specification is only as good as the knowledge of when this king reigned and for how long. One obtains a gapless relative sequence, but no single absolute fixed point.

Egyptology therefore builds its chronology in two steps. First, the relative order: Which king followed which, and how many years did each reign? For this, king lists and administrative documents serve. Then, anchoring: At which point can this chain be attached to our calendar? For this, astronomical statements or scientific dating are needed.

Classically, there is an astronomical way for anchoring, and it is worth a brief explanation because it plays a major role in older books. The Egyptian administrative calendar had 365 days without a leap day. Therefore, it drifted by one day every four years compared to the solar year, and only after about 1,460 years did both align again. If a text notes on which calendar day the star Sirius first reappeared in the morning sky after its period of invisibility, one can calculate backwards to determine in which section of this long cycle the document originated.

This is elegant and has sustained Egyptology for a long time. However, it has three weaknesses. The observation depends on the geographic latitude of the observer, and where exactly the observation took place is usually not stated; a mix-up shifts the result by decades. Because the calendar only moves one day every four years, any single observation fits four possible years. And above all: Such statements are only transmitted from the Middle Kingdom onwards.

Thus, this path is of no use for the Pyramids of Giza. The Old Kingdom lies before the first usable astronomical anchor. One must calculate the chain backwards from later epochs, and every uncertainty along the way carries over.

Every error in the first step shifts everything that lies before it. And because the Old Kingdom stands at the very beginning of the chain, all uncertainties of all later epochs accumulate there.

A tattered papyrus in Turin

The most important source for the first step is a tattered piece of papyrus in Turin.

The Turin King List Papyrus dates from the New Kingdom, more than a thousand years after the construction of the pyramids, and lists the rulers of Egypt with their reign durations. It is the most complete surviving list of its kind. It is also heavily damaged: The document was brought to Europe in fragments in the 19th century and further destroyed in the process, so that at many places exactly the numbers that matter are missing.

For Khufu, this papyrus names around 23 reign years. This number was long the basis of all calculations and is indirectly contained in the figure 2,560 BC.

In addition, there are two other traditions that should be known because they are constantly cited. Manetho, an Egyptian priest of the Ptolemaic period, wrote a history of Egypt in Greek and gives Khufu 63 years. Herodotus, even earlier, names 50. Both wrote more than two thousand years after the events, both are preserved only in quotes by even later authors, and both contradict the archaeological evidence in many places. As a source for the Old Kingdom, they are hardly suitable, but very much so as proof of what antiquity itself believed.

Thus, the calculation rests on a single serious leg: the 23 years from Turin. And precisely this leg has wobbled in recent years.

The livestock count on which chronology hangs

The reason is an administrative process that sounds harmless but is critical for chronology: the livestock count.

In the Old Kingdom, the country's livestock was periodically recorded as the basis for taxes. Because this was a large, nationwide event, the administration used it for dating. Documents bear specifications like "Year of the seventh count" or "Year after the thirteenth count." For the officials, this was unambiguous. For us, it is translatable into regnal years only if we know the interval at which counting occurred.

And we do not know this with certainty. There are indications of an annual count and indications of a biennial count, and practice seems to have changed over time. If the count was annual, the thirteenth count corresponds roughly to the thirteenth regnal year. If it was biennial, it corresponds to approximately the twenty-sixth.

This is the point at which the chronology of the Old Kingdom diverges. The same inscription means either one thing or double depending on the assumption. For a single king, this makes a decade; over an entire dynasty, it adds up to centuries.

Complicating matters is that the practice apparently changed. For some reigns, the surviving counts suggest a biennial rhythm; for others, the intervals rather suggest an annual survey; and for yet others, the data situation is too thin for a statement. A uniform rule that could be applied to all kings does not exist. Each reign must be assessed individually, and for most kings of the Old Kingdom, there are simply too few dated documents available for this.

Specifically for Khufu: In the papyri from Wadi al-Jarf, there is a dating to the year after the thirteenth count. Assuming a biennial count, this results in at least 26 or 27 regnal years, thus significantly more than the 23 from Turin. Additionally, there is a graffito from one of the relieving chambers above the king's chamber that mentions an even higher count. If this is also read as biennial, one would arrive at over thirty years.

Why the radiocarbon data are not sharper

The question remains: Why not simply anchor the chain scientifically and avoid the whole dispute?

One does this, and it works, but not with the sharpness that many expect. Between 1984 and 1995, over five hundred organic samples from structures of the Old and Middle Kingdoms were dated, predominantly charcoal and plant remains from the mortar. The results averaged one hundred to two hundred years above the historically derived data and varied considerably. Alone for the Great Pyramid of Giza, the individual values distributed over a span of around four hundred years.

Part of this is explainable. Burning old wood dates the wood, not the construction site. The specialists involved, however, held this old wood effect to be insufficient explanation themselves, because hardly continuously century-old material could have been burned.

At this point, many ask why one does not simply count tree rings. Dendrochronology elsewhere provides day-precise dating by linking ring patterns of trees over millennia. In Egypt, this does not work. There are hardly any native trees with usable annual rings because the climate does not force pronounced growth pauses, and the imported building timber comes from Lebanon, where a continuous reference curve for this time is lacking. Exactly the procedure that would answer the question in an afternoon is unavailable here. How difficult calibration is in the Nile Valley has been documented by radiocarbon research in Oxford for decades.

A significantly further approach was presented in 2010 in the journal Science. Instead of arbitrary organic remains, exclusively short-lived plant parts were dated, i.e., material that grew and was consumed in the same year, from find contexts that can be assigned to a specific reign. Over two hundred such measurements were subsequently fed into a statistical model that considered the transmitted reign durations as an additional condition. The result of this work reduces uncertainty in some places to less than twenty years.

For the Old Kingdom, this approach yields values that tend to be slightly older than the classic historical estimate. It thus confirms the magnitude and shifts the fine-tuning. That Egypt in the Nile Valley also shows a small systematic offset due to the growth time of plants is another example of how many corrections are hidden in an apparently simple year number.

Stefan C. Asafti

The discovery at Wadi al-Jarf

The strongest anchor so far was provided by a discovery no one expected, namely not in Giza, but around two hundred kilometers away at the Red Sea.

In 2013, a French-Egyptian team uncovered the oldest written papyri of Egypt in ancient harbor galleries at Wadi al-Jarf. Among them is the service book of an inspector named Merer. He noted over months how his team brought limestone blocks from the quarries of Tura to Giza by boat, with dates, quantities, and destinations.

The value of this find for dating is hard to overestimate. For the first time, a document exists that was written during the construction, was involved in the construction site, and bears a date itself. All other sources are either much later or carry no date.

Simultaneously, this very find shows where the limits lie. Its dating reads not "in year 26," but "in the year after the thirteenth count." Thus, the oldest and best document also brings us only as far as we understand the counting method. It shifts the probable reign length of Khufu upward and confirms the epoch, but it provides no year in our calendar.

Incidentally, the papyri provide a picture of operations that no king list gives. Merer's team comprised around two hundred men. They did not just transport; they also worked on water structures and were apparently deployed at several locations. Trips to Giza took only a few days each, and there were several per month. From such information, one can extrapolate how many blocks a single crew moved in a year, yielding a more realistic image of the construction site than any total number.

This is how chronology works: A find improves resolution at one point and simultaneously reveals which assumption still holds at another.

What the ground reveals about the sequence

The question remains: Why is the sequence so much more certain than the year number? The answer lies in the ground.

The plateau is not a place where three structures stand independently next to each other. They interlock. The causeway of Khafre and the Sphinx pit are cut into areas where stones for the older structure had previously been quarried. Where one structure intervenes in the quarry area of another, the sequence is clear, entirely without a calendar. Such overlaps exist at several places on the plateau.

Additionally, there are the cemeteries. East and west of the Great Pyramid lie entire rows of mastabas, laid out in planned rows, not grown organically. They were granted to family members and high officials, and titles and names stand within them. When an official states in his tomb under which king he served, he links his tomb to a reign, and via the location of the tomb, this reign is again tied to the construction sequence of the adjacent pyramid.

The structures themselves bear clues. The Pyramid of Menkaure has a granite casing that was smoothed from bottom to top and stops abruptly in the middle of work. Such unfinished states are chronological statements: Here, something ended with the death of a patron, and what came after looks different.

Finally, style helps. Statues, reliefs, and vessel shapes change over generations in comprehensible steps. An expert can place a piece of the Old Kingdom into a sequence, even if no name is inscribed on it, similar to how furniture or cars can be assigned to a decade without a date being engraved.

From all this arises a dense network of relative relationships. It reliably says what came before what and how many generations lie in between. It only does not say when. For the when, one needs the chain of king lists, reign durations, and measured values, and this is as reliable as its weakest link allows.

Dating Khufu's structure

So, which number should you use if you need one?

For most purposes, "around 2,560 BC" is the correct answer for the Great Pyramid of Giza, and "26th century BC" is the correct answer for the entire complex. Both statements are professionally defensible, both are widespread in literature, and both already carry the ambiguity in the word "around."

For the three structures individually, the common approximations are: the Great Pyramid of Giza around 2,560 BC, the Pyramid of Khafre about a generation later, and the Pyramid of Menkaure yet another generation thereafter. If one needs a single number for the entire complex, e.g., for a caption, one is correct with "25th to 26th century BC" and needs to qualify nothing.

More important than the decimal point is the sequence, and that is secured. First the Great Pyramid of Giza, then the Pyramid of Khafre, then the significantly smaller Pyramid of Menkaure. The Sphinx belongs with high probability to the time of Khafre. The entire construction phase encompasses about three generations.

Caution is warranted as soon as someone cites a year number without "around," especially if it appears very precise. Figures like 2,560 BC are roundings of a calculation with an error margin of several decades. Whoever presents them as exact has either copied blindly or does not understand what they are quoting.

Practically, a look at the formulation helps. Museum and excavation labels usually write "around" or give a range, e.g., 2,600 to 2,500 BC, and sometimes name the underlying chronology for this. Popular presentations leave both out. If two sources differ by fifty or eighty years, they usually do not contradict each other but follow different approaches. Only with deviations of several centuries is it worthwhile checking the origin of the number.

And equally caution with much older datings. Whoever dates the complex to ten thousand or twelve thousand years must not only justify a different year number but explain why all administrative texts, king lists, worker settlements, tombs, and over four hundred radiocarbon samples should show in the same wrong direction. No one has provided this explanation so far.

Frequently asked questions

When was the Great Pyramid of Giza built?

According to common dating around 2,560 BC, during the reign of King Khufu. The figure has an error margin of several decades.

Why do different books cite different years?

Because they follow different chronologies. The differences arise primarily from the question of whether the ancient Egyptian livestock count was annual or biennial.

Can the stones themselves be dated?

No. Radiocarbon dating works only on organic material. Therefore, the charcoal in the mortar is dated, not the limestone.

In what order did the three pyramids originate?

Khufu, then Khafre, then Menkaure, within around eighty years under three successive kings.

We know the sequence better than the year

There is a sentence that does all the work on this page: We know the sequence better than the year number.

This sounds like an admission but is in truth a quite strong statement. Egyptology can say who succeeded whom, which structure arose before which, which official served under which king, and in what order the chambers of a pyramid were planned. It can do this over centuries, supported by administrative writing, tombs, and construction findings.

This sequence suffices for almost everything one wants to do with a date. It answers whether the Sphinx is older than the smallest pyramid, whether the worker settlement belongs to the construction period, whether a tomb arose before or after the structure next to it. Only the one question, which stands in the search field, does it not answer directly.

What it cannot do is nail down the same chain to our calendar without inserting an assumption at one point. And that this assumption concerns precisely the frequency of a cattle count is the most beautiful detail in the whole matter. An administrative process from the third millennium BC decides which year stands today on the sign in front of the pyramid.

If you read 2,560 BC somewhere next time, you now know what is contained in this number: a damaged king list from Turin, a service book from the Red Sea, four hundred radiocarbon samples, a statistical model, and an open question about cattle.