An important stage of planning in the implementation of IT-projects is the assessment of the complexity of software development. An accurate estimate of labor costs at the early stage of the project life cycle significantly affects the allocation of resources, time planning and budget costs. Therefore, regardless of the large number of methods used to estimate labor costs during the implementation of an IT-project, the task of increasing the accuracy of this predictive estimate is relevant. The paper examines in detail the possibilities of using the well-known method for estimating labor costs Use Case Points (UCP), which is based on the use of use cases. It belongs to algorithmic methods, which makes it quite reliable and predictable in use. It also allows you to take into account the functional requirements for the system, which is especially useful in the early stages of project implementation. In addition, UCP is not tied to specific technologies or programming languages, which indicates its universality and flexibility. The purpose of the study is to improve the UCP method of estimating labor costs necessary for the successful implementation of an IT-project, which will allow taking into account interval estimates of technical complexity factors and external factors that affect the estimation of the amount of software and, accordingly, the estimation of the project's labor intensity. To experimentally verify the operability and efficiency of the proposed modified UCP method, a dataset containing information on 71 real projects was used. The results of computer modeling and comparative analysis of the accuracy of estimates of labor costs for the implementation of the project obtained using the proposed and original UCP methods are given. The results of the experiments showed that the proposed modification of the UCP method allows obtaining more accurate predictive estimates of labor costs in the implementation of IT-projects, which can significantly affect the efficiency of planning and project management processes.