The most general surface tension estimation method is that of MacLeod and Sugden. MacLeod suggested an empirical relationship between surface tension and liquid density. Sugden later showed that the empirical constant appearing in MacLeod's formulation was identical to a constitutive constant called the parachor. The equation introduced by Sugden is:

s^1/4 = P (r_L - r _v) / M

where

s = surface tension (dynes/cm)
P = parachor
r_L = liquid density (g/cm8)
r _v = vapor density (g/cm8)
M = molecular weight (g/mol)

The parachor can be visualized as a comparative volume between two liquids and is reasonably independent of temperature. Quayle presented a comprehensive review of methods for estimating the parachor and devised one that is suitable for a wide variety of organic compounds. For most purposes r _v is so much smaller than r_L that it can be ignored.

s = (P*r_L / M )⁴

This equation is the basic equation for surface tension estimation.
Errors typically average 5%, but individual values can deviate as much as 30% from measured values.

This JAVA applet predict liquid density with using neural network method.
ex.
CH3COOC2H5
P=214.8
M=88.107
Density=0.90063
s = (P*r_L / M )⁴= (214.8*=0.90063 / 88.107 )⁴=23.24 dyne/cm

Experimental value of surface tension is 23.97 dyne/cm at 20'C

This method is very sensitive to Liquid Density.
Density fluctuate -3% (0.90063 -> 0.874 ) s =20.58 dyne/cm (-14%)
Density fluctuate +3% (0.90063 -> 0.928 ) s =26.16 dyne/cm (+9%)

Van Krevelen method is developed for polymer surface. This method is also sensitive for density.