An experimental apparatus was designed to measure accurately the density of supercritical CO2 in wide temperature and pressure ranges. Based on experimental results, the curves for CO2 density as function of pressure at certain temperatures were divided into linear-growth, rapid-growth, and slow-growth intervals. The relative error between the experimental and calculated density values for a number of frequently used equations of state was evaluated. These equations were corrected after analyzing the accuracy of each equation in the different intervals. A new method for calculating the density of supercritical CO2 that includes 28 constant parameters is proposed to determine the density at a known temperature and pressure.