Does anybody know the compressibility constant of water and air?

 

I think water is incompressible

 

Nothing is truly incompressible, although many liquids can be treated as such as a simplifying assumption in most cases.

 

I agree with Dana.
For your calculation you can consider the water as incompressible.

 

It depends on what he's trying to calculate, and what kinds of pressures are involved. For example, in subsonic aerodynamics, even air is generally treated as incompressible, though obviously it's not.

As far as the actual values the OP is looking for, I don't know off the top of my head, but google is your friend.

 

Almost everything can be compressed, even things that are said to be 'uncompressible', for example mineral hydraulic oil on average compresses by 0.5% for every 1,000psi or 0.007%/Bar.

Water compresses by 0.004%/Bar and air by a staggering 100%/Bar, that's why an air receiver holds so much air.

An air receiver charged to 8 Bar holds 8 times the volume of the receiver.