The coagulation rate is an important parameter for colloids, which is very useful for evaluating the colloidal stability. Both static light scattering and dynamic light scattering are commonly used methods for measuring the coagulation rate. By using these methods, the light scattering properties of single particles and aggregates of two particles are needed. Therefore, one may need both the static and dynamic light scattering data to avoid the calculation of the relevant scattering properties. Usually, when only static or dynamic light scattering data are available, various approximations are used to solve the problems related to the light scattering properties of particles and aggregates. However, due to the limitation of size and shape of colloidal particles in these approximations, the results were not always satisfactory. Since the T-matrix method can be used to precisely calculate the characteristic of light scattering without approximation of particle size or shape, we use this method in the determination of coagulation rate in static or dynamic light scattering measurement in this study. The comparison of our results with those measured by simultaneous static and dynamic light scattering method confirms that the T-matrix method is suitable for the light scattering measurement of coagulation rate. Therefore, this study simplifies the coagulation rate measurement by light scattering methods and extends their applications.