Numerical calculations were conducted to calculate the heat conduction rate between soot (carbon) aggregates of different sizes and the surrounding gas in the free-molecular regime using the direct simulation Monte Carlo method. This method is based on simulation of the trajectories of individual molecules and calculation of the heat transfer at each of the molecule/molecule collisions and the molecule/particle collisions. Soot aggregates of known fractal dimension and pre-factor are first numerically generated using a cluster-cluster aggregation algorithm. Effect of incomplete thermal accommodation was accounted for by employing the Maxwell gas-surface interaction model. Gas collisions were treated using the simple hard sphere model. Numerical results were obtained for aggregate sizes between 10 and 228 primary particles and the thermal accommodation coefficient between 0.1 and 1. A simple scaling for the heat transfer equivalent sphere diameter was also presented for incorporation into a laser-induced incandescence model.