The methods of histograms and cumulants’ have been applied to extract temperature dependent information from dynamic simulations of polyethylene. The use of these methods allows one to efficiently predict the coefficients of thermal expansion, and for the latter method, even to determine their temperature dependence from relatively short simulations. Using standard force fields and a run of only 470 ps, the latter method matches the coefficients of thermal expansion to 6% for the a unit cell dimension, 2% for b and 50% for the quite small, negative, coefficient in the c-dimension.