  Various approaches to quantum gravity suggest that the fundamental volume of
the phase space of the given space for representative points, means !0, should
be modified. In this paper, we study the effects of this modification on the
thermodynamics of an ideal gas within the micro canonical ensemble. For this
end, we use a Generalized Uncertainty Principle (GUP) that admits both a
minimal measurable length and a maximal momentum. Using this GUP causes
decreasing the total number of the microstates of the system. In the first
step, we calculate these reductions for classical ideal gas, and in the second
step, we calculate these effects for ultra relativistic gas.
