To predict the safe operational service life (safe use time) and the safe service life in storage (safe storage time) of gun propellants (GP) and rocket propellants (RP) the consumption of stabilizer is often used. For this the measured data must be described with a kinetic model. Frequently an exponential decrease of the stabilizer content is taken, which corresponds to a reaction of first order. But the exponential decrease reproduce the measured stabilizer content below 30 % of the original content not good, the deviation can be considerable. Moreover the times to reach a stabilizer content of zero are infinite, which is not in accordance to reality. An equation is given. which describes the consumption of stabilizers such as diphenylamine, 2-nitro-diphenylamine, acardite II and ethylcentralite very well. The equation was obtained with a kinetic formulation, which combines the reactions of first and zero order. According to this model, the times up to a complete consumption of the s tabilizer are finite and can be calculated with the reaction rate constants of the model. The prediction of the life time is considerably improved, especially for small degrees of stabilizer content y(ind s) = S(t)/S(O). This new equation for the stabilizer consumption allows a normalized representation of the stabilizer decrease, which can reveal mechanistic changes in the course of the reaction. The kinetic formulation is not specific to any stabilizer, so the equation can be used for other stabilizers also.