This is the second of two articles which aim to provide children's nurses with an opportunity to develop their knowledge and skills of medicines management when caring for children and young people. The first article considered the processes associated with effective medicines management, including the concept of human error. This article addresses essential numeracy and calculation skills that have been identified as an important risk factor associated with medication errors in children. The range of activities throughout the article will help you develop and practise numeracy skills, with the answers for each activity at the end of the article.