  Frequency combs have revolutionized optical frequency metrology, allowing one
to determine highly accurate transition frequencies of a wealth of molecular
species. Despite a recognized scientific interest, these progresses have only
marginally benefited infrared-inactive transitions, due to their inherently
weak cross-sections. Here we overcome this limitation by introducing
stimulated-Raman-scattering metrology, where a frequency comb is exploited to
calibrate the frequency detuning between the pump and Stokes excitation lasers.
We apply this approach to molecular hydrogen to test quantum electrodynamics.
We measure the transition frequency of the Q(1) fundamental line of H$_2$
around 4155 cm$^{-1}$ with few parts-per-billion uncertainty, which is
comparable to the theoretical benchmark of ab initio calculations and more than
a decade better than the experimental state of the art. Our comb-calibrated
stimulated Raman scattering spectrometer extends the toolkit of optical
frequency metrology as it can be applied, with simple technical changes, to
many other infrared-inactive transitions, over a 50-5000 cm$^{-1}$ range that
covers also purely rotational bands.

Optics;Instrumentation and Detectors