A-values are numerical values used in the determination of the most stable orientation of atoms in a molecule, as well as a general representation of steric bulk. A-values are derived from energy measurements of the different cyclohexane conformations of a monosubstituted cyclohexane chemical. Substituents on a cyclohexane ring prefer to reside in the equatorial position to the axial. The difference in Gibbs free energy (ΔG) between the higher energy conformation and the lower energy conformation is the A-value for that particular substituent.