We calculated the free energy of vapor phase nucleation in a truncated and shifted Lennard-Jones fluid by subjecting a small system taken inside the metastable phase to grand canonical Monte Carlo simulation and then estimating the probability distribution over the macrostates specified by global order parameters. The free energy surface determined by this method exhibits a strong dependence on the system volume. Despite this, the free energetics relevant to the prediction of steady-state nucleation rate is shown to remain unchanged over a wide range of the system size. (C) 2003 American Institute of Physics.