how many of earth's atmospheres is on you at sea level?

Answer 1

http://csep10.phys.utk.edu/astr161/lect/earth/atmosphere.html

Answer 2

is it possible to give a number answer?

Answer 3

Yes. See the map in the link above. Count the layers over the earth.

Answer 4

is it 4?

Answer 5

Yes. :-)