We calculate the pressure (p), the energy density (\epsilon) and the
baryon density (n_B) of QCD at finite temperatures (T) and chemical
potentials (\mu). The recently proposed overlap improving multi-parameter
reweighting technique is used to determine observables at nonvanishing
chemical potentials. Our results are obtained by studying n_f=2+1 dynamical
staggered quarks with semi-realistic masses on N_t=4 lattices.