A criterion for predicting the transverse spacing dimensions in gas phase detonations is developed. The criterion depends upon the collision of wave fronts to form new reaction centers which eventually lead to the formation of new cells. Calculated values of transverse spacing over a wide range of pressure, dilution and degree of overdrive in the hydrogen‐oxygen‐argon system are compared to experimental data for stoichiometric mixtures. The predicted values of spacing with no overdrive are about twice the experimental values. A minimum in the predicted spacing is found with overdrive as well as a cutoff value of overdrive for which the predicted spacing becomes infinite.