The formation of the skill of mental counting is one of the main tasks of elementary school. It is in the first years of education that children learn the basic techniques of oral calculations.. Therefore, it is very important to pay special attention to developing this skill.The manual presents all types of tasks aimed at developing the skill of mental counting.Different types of exercises are given: finding the values of mathematical expressions, solving equations, solving problems.The following forms of work with tasks are possible:fluent auditory|visual| combined.To achieve the correctness and fluency of oral calculations, it is necessary to devote 5–10 minutes to mental counting every day. Examples and tasks of the book will help the child to work out and consolidate the skills of mental counting to automaticity, activate mental activity, develop memory, attention and speed of reaction.The book was prepared in accordance with the requirements of the Federal State Educational Standard of Primary Education. It can be used when working with any textbook included in the Federal List. The manual will be useful in mathematics lessons and for self-study at home.