  The maximal gravitational mass of nonrotating neutron stars ($M_{\rm TOV}$)
is one of the key parameters of compact objects and only loose bounds can be
set based on the first principle. With reliable measurements of the masses
and/or radii of the neutron stars, $M_{\rm TOV}$ can be robustly inferred from
either the mass distribution of these objects or the reconstruction of the
equation of state (EoS) of the very dense matter. For the first time we take
the advantages of both two approaches to have a precise inference of $M_{\rm
TOV}=2.25^{+0.08}_{-0.07}~M_\odot$ (68.3\% credibility), with the updated
neutron star mass measurement sample, the mass-tidal deformability data of
GW170817, the mass-radius data of PSR J0030+0451 and PSR J0740+6620, as well as
the theoretical information from the chiral effective theory ($\chi$EFT) and
perturbative quantum chromodynamics (pQCD) at low and very high energy
densities, respectively. This narrow credible range is benefited from the
suppression of the high $M_{\rm TOV}$ by the pQCD constraint and the exclusion
of the low $M_{\rm TOV}$ by the mass function. Three different EoS
reconstruction methods are adopted separately, and the resulting $M_{\rm TOV}$
and $R_{\rm TOV}$ are found to be almost identical, where $R_{\rm
TOV}=11.90^{+0.63}_{-0.60}$ km is the radius of the most massive non-rotating
NS. This precisely evaluated $M_{\rm TOV}$ suggests that the EoS of neutron
star matter is just moderately stiff and the $\sim 2.5-3M_\odot$ compact
objects detected by the second generation gravitational wave detectors are most
likely the lightest black holes.
