Diversification of production is a necessary step for the further development of the enterprise. After all, it facilitates the process of diversification into new markets, the choice of new and more effective business strategies to stabilize the activity of the enterprise, reduce the overall level of risk. It is very important to choose the most effective strategy for the diversification of production. Therefore it is necessary to adequately assess the overall situation in the market. Typically, such an assessment is carried out in conditions of lack of information, which determines the use of the interval values for the calculations required quantities. From this it follows that it is the use of interval model of market capacity allows more adequately assess the situation on the market in terms of lack of information. The article was used interval model of market capacity. Practical application of the model is demonstrated by the example of the market climate systems for the determination of market size for the two product lines. Was performed a comparative evaluation of the market capacity for product lines, based on what was chosen the most effective options strategies for diversification.