We present a molecular coarse-graining approach applied to polystyrene which obtains both the bonded and nonbonded interactions of the coarse-grained model from the sampling of isolated atomistic chains and pairs of oligomers. Atomistic melt properties are not used in the parametrization. We show that the coarse-grained polystyrene model not only predicts melt properties, including the melt packing and the density between 400 and 520 K, in satisfactory agreement with the atomistic model, but also reproduces the local chain conformations of atactic as well as stereoregular polystyrene. The model takes into account and reproduces correlations between neighboring bonded degrees of freedom and therefore reproduces the conformations of detailed atomistic chains in the melt on all length scales.