# How much steric hindrance does a phenyl group offer?

I've come across a question in my revision in which I am asked to compare the steric hindrance provided by a number of substituents. Those relating to phenyl are ranked relatively low, despite it being what I thought was a rather large substituent. Is this due to the planarity of the ring, or is it just much smaller than I originally thought; does a tertiary alkyl substituent provide more steric hindrance because it is larger, or because it is spread in all directions?

The larger the A-Value, the larger the substituent and the greater its preference for the equatorial location ($\mathrm{\Delta G = -RTlnK_{eq}}$ where $\mathrm{K_{eq}}$ represents the the axial/equatorial ratio at equilibrium).