2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/23196We present the q-Stirling's formula using the q-product determined by Tsallis entropy as nonextensive generalization of the usual Stirling's formula. The numerical computations and the proof are also shown. Moreover, we derive and prove some inequalities and equalities concerning the q-Stirling's formula. Applying the q-Stirling's formula, the mathematical foundations of Tsallis statistics can be obtained as similarly as those of Boltzmann-Gibbs statistics.17 pages, submittedStatistical Mechanicstext