The implosion of a family of reactor‐size targets for inertial confinement fusion (ICF) is studied analytically and numerically. The targets consist of a deuterium–tritium (D–T) shell filled with D–T vapor and they are imploded by a multistep pressure pulse designed in such a way that the final hot spot is formed mainly from the initially gaseous fuel. The formation of the hot spot is described by means of a relatively simple model, and scaling laws for the quantities that characterize the state of the initially gaseous part of the fuel prior to ignition are derived. The results of the model are compared with one‐dimensional fluid simulations, and good agreement is found. A parametric study of the fuel energy gain is then presented; the dependence of the gain and of the hot spot convergence ratio on the pulse parameters and on the filling gas density is analyzed. It is also shown that a substantial increase in the gain (for a given target and pulse energy) can be achieved by replacing the last step of the pulse with an exponential ramp.