Cell growth inhibition is generally handled as a measure of toxicity. Shortly, more toxicity implies more growth inhibition. Then, the question arises; How to calculate & evaluate cell growth inhibition in a universal manner? Actually, the method for calculating growth inhibition is not considered to be a central issue, in general. There are various approaches for calculating cell growth. Among these approaches, two of them are highly easy and popular, subtraction-based and division-based calculations. However, these two methods for the calculation of cell growth do not strongly reflect the nature of cell growth. Alternatively, the use of a doubling number-based formulation can provide a better approach and performance in the evaluation of cell growth and cell growth inhibition unless the culture attains the confluent status. Here, we discussed different methods of growth calculation which we applied to the study of “growth inhibition of BY-2 cells under Cd exposure”.