  The quantum gravitational scale of inflation is calculated by finding a sharp
probability peak in the distribution function of chaotic inflationary
cosmologies driven by a scalar field with large negative constant $\xi$ of
nonminimal interaction. In the case of the no-boundary state of the universe
this peak corresponds to the eternal inflation, while for the tunnelling
quantum state it generates a standard inflationary scenario. The sub-Planckian
parameters of this peak (the mean value of the corresponding Hubble constant
${\mbox{\boldmath $H$}}\simeq 10^{-5}m_P$, its quantum width
$\Delta{\mbox{\boldmath $H$}}/{\mbox{\boldmath $H$}}\simeq 10^{-5}$ and the
number of inflationary e-foldings ${\mbox{\boldmath $N$}}\simeq 60$) are found
to be in good correspondence with the observational status of inflation theory,
provided the coupling constants of the theory are constrained by a condition
which is likely to be enforced by the (quasi) supersymmetric nature of the
sub-Planckian particle physics model.
