A new method for the measurement of gas adsorption at high pressure is described in detail. The method is based on dielectric virial coefficients and it takes advantage of the dielectric technique for the accurate measurement of the compressibility factor of gases at high pressure. The method is simple, self‐sufficient, easy to use, and permits precise measurement of the density of nonideal gases. Adsorption measurements of methane on BPL‐activated carbon as a function of pressure at 25 °C are reported.