Coking pressure was measured at varying expansion degrees of carbonized coal samples. The degree of expansion at which the laboratory coking pressure was identical with that observed in an oven with a movable wall, was assumed to equal the degree of expansion of the plastic layer formed by the shrinking coke and semi-coke layers in the coke chamber. Again, the layer expansion capacity in a coke chamber was assumed to be proportional to the shrinkage determined in a Sapozhnikov standard test. Results of laboratory measurements were consistent with those obtained on a semitechnical scale, measured on coking a black coal in an oven with a movable wall which, in turn, were close to the coking pressures prevailing in commercial coking chambers.