Nuclear level densities for Fe-56,Fe-57 have been extracted from the primary gamma-ray spectra using (He-3, He-3(')gamma) and (He-3, alpha gamma) reactions. Nuclear thermodynamic properties for Fe-56 and Fe-57 are investigated using the experimental level densities. These properties include entropy, Helmholtz free energy, caloric curves, chemical potential, and heat capacity. In particular, the breaking of Cooper pairs and single-quasiparticle entropy are discussed and shown to be important concepts for describing nuclear level density. Microscopic model calculations are performed for level densities of Fe-56,Fe-57. The experimental and calculated level densities are compared. The average number of broken Cooper pairs and the parity distribution are extracted as a function of excitation energy for Fe-56,Fe-57 from the model calculations.