A simple and new method for the accurate prediction of the hydrogen content of petroleum fractions is presented. The new method is inferred from the concept of the molar additivity of the structural contributions of the carbon types in the average hydrocarbon molecule. It requires only basic physical properties such as the density and refractive index at 20 degrees C, and the 50 wt % true boiling point. The influence of heteroatoms and olefinic bonds was found to be largely implicit, except for oxygen. By its fundamental basis this new correlation features an unparalleled precision equivalent to that of the most accurate but time-consuming analytical methods. This is demonstrated by an included data set.