The reaction thermodynamics of metal hydrides are crucial to the use of these materials forreversible hydrogen storage. In addition to altering the kinetics of metal hydride reactions,the use of nanoparticles can also change the overall reaction thermodynamics. We usedensity functional theory to predict the equilibrium crystal shapes of seven metals andtheir hydrides via the Wulff construction. These calculations allow the impact ofnanoparticle size on the thermodynamics of hydrogen release from these metal hydrides tobe predicted. Specifically, we study the temperature required for the hydride to generate aH2 pressure of 1 bar as a function of the radius of the nanoparticle. In most, but not all, casesthe hydrogen release temperature increases slightly as the particle size is reduced.