An introductory lesson to binary/denary conversion. The lesson gives pupils the opportunity to convert denary to binary and vice versa. As well as the activities included on the slides, the lesson comes with a pupil worksheet. The lesson is designed for KS3 but could also be used as an introductory lesson at KS4. The lesson gives teacher demonstrations before pupils work independently. All answers to the activities including the worksheet are provided. The lesson also introduces the vocabulary of binary, denary, and hexadecimal (although hex is not explored further during this particular lesson). In addition to the slides and the worksheet, pupils will need a mini whiteboard and their exercise book. Teacher notes are included on each slide so that the lesson can be picked up and delivered by any teacher or cover supervisor.