The density of carbonated water is dependent on the degree of carbonation. There is no consistent density for carbonated water, however, if you know the variables you can easily calculate the density.
In order to calculate the density of carbonated water, you need the density of both carbon dioxide and water. Carbon dioxide has a density of .00198 g/cm cubed. The density of water is 1 g/cm cubed.
The equation to calculate the density of a substance involves multiplying the percentage of concentration of one substance by its density and adding it to the percentage times density of the other substance.
If the concentration of carbon dioxide in carbonated water is 1 percent, you can calculate the density using the formula: .01 x .00198 g/cm^3 + .99 x 1 g/cm^3 = .9900198 g/cm^3 In this case the density of the carbonated water is .9900198 g/cm^3.