How tall were the Nephilim and the giants?

The Nephilim and the giants stood three thousand ells tall. The Book of Enoch records that the wives taken by the Watchers became pregnant and bare great giants whose height was three thousand ells (1 Enoch 7:2).

These colossal offspring of the Watchers and human women consumed all the acquisitions of men. When humans could no longer sustain them the giants turned against mankind, devoured people, sinned against animals, and finally began to devour one another's flesh and drink the blood (1 Enoch 7:3-5).

Their immense size and unchecked appetite thus became a central cause of the lawlessness that filled the earth before the Flood (1 Enoch 7).