# When exactly was it built, and how long did it take? · How the Great Pyramid was built > Two answers have been proposed. Built within Khufu's reign of about 26 years or more, in the 26th century BC. leads, with evidence 2 for, 1 against… Source: https://mysteriesdept.com/mysteries/great-pyramid/questions/QST0CSMNVZR2ZYC/when-exactly-was-it-built-and-how-long-did-it-take Publisher: Mysteries Department Licence: CC BY 4.0 (credit Mysteries Department and link the page) Updated: 2026-10-26T11:57:32+00:00 --- **0** # When exactly was it built, and how long did it take? Asked 26 Oct 2026 by [**apollo** ](https://mysteriesdept.com/u/apollo)·Part of [Who built the Great Pyramid, and how was the work organised?](https://mysteriesdept.com/mysteries/great-pyramid/questions/QST0CSMNV8A4GQV/who-built-the-great-pyramid-and-how-was-the-work-organised)·2 answers·0·0 following **Answered: Built within Khufu's reign of about 26 years or more, in the 26th century BC.** Passed its tests and review. ## Where it stands Two answers have been proposed. Built within Khufu's reign of about 26 years or more, in the 26th century BC. leads, with evidence 2 for, 1 against: supported by its tests. One is still possible. ## Why it matters The build time sets the labour arithmetic; the radiocarbon offset has been used to argue for an earlier date⁠[[1]](https://mysteriesdept.com/sources/SRC0CSMNKP45WQJ/radiocarbon-dates-of-old-and-middle-kingdom-monuments-in)⁠[[2]](https://mysteriesdept.com/sources/SRC0CSMNKXY3QR1/radiocarbon-based-chronology-for-dynastic-egypt). ## Answers 2 [**Built within Khufu's reign of about 26 years or more, in the 26th century BC.** ](https://mysteriesdept.com/mysteries/great-pyramid/answers/ANS0CSMP5R85KXV/built-within-khufus-reign-of-about-26-years-or-more-in-the) Supported by its tests Evidence: 2 for, 1 against Most likely [**None of these.** ](https://mysteriesdept.com/mysteries/great-pyramid/answers/ANS0CSMP6QG2SP0/none-of-these) Failed a test; not refuted outright Evidence: none yet Disputed ## History 1. 2001[Bonani et al.: mortar dates from the pyramid itself average 100 to 200 years older than the historical date.](https://mysteriesdept.com/sources/SRC0CSMNKP45WQJ/radiocarbon-dates-of-old-and-middle-kingdom-monuments-in)Against: Built within Khufu's reign of about 26 years or more, in the 26th century BC. 1. 2010[Bronk Ramsey et al. puts forward: built within Khufu's reign of about 26 years or more, in the 26th century BC.](https://mysteriesdept.com/sources/SRC0CSMNKXY3QR1/radiocarbon-based-chronology-for-dynastic-egypt) 1. 2010[Bronk Ramsey et al.: the Oxford model agrees with the historical chronology within decades.](https://mysteriesdept.com/sources/SRC0CSMNKXY3QR1/radiocarbon-based-chronology-for-dynastic-egypt)For: Built within Khufu's reign of about 26 years or more, in the 26th century BC. 1. 2017[Tallet: year 26 is the last attested year of Khufu and the pyramid was receiving casing stone then.](https://mysteriesdept.com/sources/SRC0CSMNFHA1XVA/les-papyrus-de-la-mer-rouge-i-le-journal-de-merer-papyrus)For: Built within Khufu's reign of about 26 years or more, in the 26th century BC. 1. 26 Oct 2026Asked on this site ## Discussion 0 [Add to the discussion](https://mysteriesdept.com/signin?next=/mysteries/great-pyramid/questions/QST0CSMNVZR2ZYC/when-exactly-was-it-built-and-how-long-did-it-take%23discussion) Help with this question [ **Propose an answer** Something the evidence could support or rule out ] [ **Propose an answer** Something the evidence could support or rule out ](https://mysteriesdept.com/signin?next=/mysteries/great-pyramid/questions/QST0CSMNVZR2ZYC/when-exactly-was-it-built-and-how-long-did-it-take%23add-answer) [ **Add evidence** A result for or against an answer ] [ **Add evidence** A result for or against an answer ](https://mysteriesdept.com/signin?next=/mysteries/great-pyramid/questions/QST0CSMNVZR2ZYC/when-exactly-was-it-built-and-how-long-did-it-take%23add-evidence) [ **Ask a sub-question** A smaller question that would help settle this one ] [ **Ask a sub-question** A smaller question that would help settle this one ](https://mysteriesdept.com/signin?next=/mysteries/great-pyramid/questions/QST0CSMNVZR2ZYC/when-exactly-was-it-built-and-how-long-did-it-take%23add-question) [ **Add a source** A paper, archive record or image ] [ **Add a source** A paper, archive record or image ](https://mysteriesdept.com/signin?next=/mysteries/great-pyramid/questions/QST0CSMNVZR2ZYC/when-exactly-was-it-built-and-how-long-did-it-take%23add-source) Where it fits How the Great Pyramid was built [**Who built the Great Pyramid, and how was the work organised?** ](https://mysteriesdept.com/mysteries/great-pyramid/questions/QST0CSMNV8A4GQV/who-built-the-great-pyramid-and-how-was-the-work-organised)Key question · A rotating, provisioned Egyptian workforce of about 20,000 to 25,000 under royal officials built it during… [How did the stone reach the plateau?](https://mysteriesdept.com/mysteries/great-pyramid/questions/QST0CSMNVQY7M8Q/how-did-the-stone-reach-the-plateau)Answered · Boats brought Tura limestone and Aswan granite along a Nile branch and canals to a harbour at the foot of the… **When exactly was it built, and how long did it take?** You're here · Built within Khufu's reign of about 26 years or more, in the 26th century BC. 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