The stone that hit me was as large as an egg.可以改为“The stone that hit me was about _ _ _an egg.

The stone that hit me was as large as an egg.可以改为“The stone that hit me was about _ _ _an egg.
The stone that hit me was as large as an egg.可以改为“The stone that hit me was about _ _ _an egg.

The stone that hit me was as large as an egg.可以改为“The stone that hit me was about _ _ _an egg.
the size of
The stone that hit me was about （the) （size）（of) an egg.
希望帮到了你

“The stone that hit me was about the same as an egg.

The stone that hit me was about 【the size as】an egg.

个人意见，希望可以帮助到你。