  Using multi-frequency spectra from TeV blazars in quiescent states, we obtain
the physical parameters of the emission region of blazars within the framework
of the one-zone synchrotron self-Compton (SSC) model. We numerically calculate
the steady-state energy spectra of electrons by self-consistently taking into
account the effects of radiative cooling with a proper account of the
Klein-Nishina effects. Here electrons are assumed to be injected with a
power-law spectrum and to escape on a finite time scale, which naturally leads
to the existence of a break energy scale. Although we do not use time
variabilities but utilize a model of electron escape to constrain the size of
the emission region, the resultant size turns out to be similar to that
obtained based on time variabilities. Through detailed comparison of the
predicted emission spectra with observations, we find that for Mrk 421, Mrk
501, and PKS 2155--304, the energy density of relativistic electrons is about
an order of magnitude larger than that of magnetic fields with an uncertainty
within a factor of a few.
