The maximum masses for both of these is 1.4 times the Sun, but if they are rotating, they can have masses up to twice this 'Chandrasekhar/Oppenheimer- Volkov' limit. I believe that the lower mass limits for white dwarfs are near 0.7 solar masses, but for neutron stars I do not know if there are reliable estimates because to get them they would have to be members of binary stars. The famous Taylor-Hulse binary pulsar has individual neutron star masses near 1.2 times the mass of the Sun or there abouts.