How many years did it take to build the Great Pyramid of Giza, according to the consensus of Egyptologists?

Answer

20 years

Roughly 20 years to place millions of multi-tonne blocks means setting a block every few minutes, around the clock. The workforce wasn't slaves but rotating crews of paid laborers who were fed remarkably well — archaeologists found evidence of massive beef consumption at the workers' village.

Source: Mark Lehner / AERA excavations at Giza (via PBS NOVA)