QCD equation of state to O(mu(6)(B)) from lattice QCD

We calculated the QCD equation of state using Taylor expansions that include contributions from up to sixth order in the baryon strangeness and electric charge chemical potentials. Calculations have been performed with the Highly Improved Staggered Quark action in the temperature range T epsilon [135 MeV 330 MeV] using up to four different sets of lattice cutoffs corresponding to lattices of size N sigma 3x N tau with aspect ratio N sigma/N tau = 4 and N tau=6-16. The strange quark mass is tuned to its physical value and we use two strange to light quark mass ratios ms/ml = 20 and 27 which in the continuum limit correspond to a pion mass of about 160 and 140 MeV respectively. Sixth order results for Taylor expansion coefficients are used to estimate truncation errors of the fourth order expansion. We show that truncation errors are small for baryon chemical potentials less then twice the temperature (mu(B) 0.9.