The total internal partition sum, Q_int(T), and the translational partition sum, Q_trans(T), were computed for six isotopologues of NO: ¹⁴N¹⁶O, ¹⁵N¹⁶O, ¹⁴N¹⁸O, ¹⁴N¹⁷O, ¹⁵N¹⁸O, ¹⁵N¹⁷O. These were used to determine the total partition sum, Q(T), and its first and second moments, and ⁠. The total internal partition sum was computed using term values determined by Qu et al. [Mon. Not. R. Astron. Soc. 504, 5768–5777 (2021)] for ¹⁴N¹⁶O and those of Wong et al. [Mon. Not. R. Astron. Soc. 470, 882–897, (2017)] for the other isotopologues. These term values are the best available and hence provide the most accurate total internal partition sums and its first and second moments. The uncertainties in Q_int(T), its moments, and the resulting thermodynamic functions were determined from the uncertainty in the term values and the uncertainty due to the convergence of the partition sum and its moments. From these quantities, the isobaric heat capacity, Helmholtz energy, entropy, enthalpy, Gibbs function, and the JANAF functions hef and gef, and their uncertainties, were computed on a 1 K grid from 1 to 9000 K. The data are compared with the literature values. The resulting thermodynamic quantities are the most accurate determined from
direct summation of Q(T), ˜Q ′(T), and ˜Q ′′(T).