  We compute the pressure of the standard model at high temperatures in the
symmetric phase to three loops, or to O(g^5) in all coupling constants. We find
that the terms of the perturbative expansion in the SU(2) + Higgs sector
decrease monotonically with increasing order, but the large values of the
strong coupling constant g_s and the Yukawa coupling of the top quark g_Y make
the expansion in the full theory converge more slowly. The final result is
observed to be about 10% smaller than the ideal gas pressure commonly used in
cosmological calculations.
