have one’s head in the clouds

(idiom) to be separate from reality, to dream

Example Sentences:

My brother has his head in the clouds if he thinks he is going to become an Engineer, because he is terrible at math.

A: I hope to be rich by the time I am 30.
B: How old are you now?
A: 29.
B: Wow. You have your head in the clouds! That’s going to be impossible!

From the Blogs:

HP sticks its head in the clouds

Media:

Similar idioms:

1. get one’s head around
2. be banging one’s head against the wall
3. beat one’s head against the wall
4. hit the nail on the head
5. have a good head on one’s shoulders
6. head for
7. over one’s head
8. head start
9. hang one’s head