Bicycling is a popular activity for children. In order for children to enjoy cycling and to minimize injury, it is important that they are positioned appropriately on the bicycle. The purpose of this study was therefore to identify a suitable bicycle setup for children aged between 7 and 16 years which accommodates developmental differences in anthropometrics, flexibility and perceptions of comfort. Using an adjustable bicycle fitting rig, we found the most comfortable position of 142 children aged 7 to 16. In addition, a number of anthropometric measures were recorded. Seat height and the horizontal distance between seat and handlebars were strongly predictable (R > 0.999, p < 0.001 and R = 0.649, p < 0.001 respectively), whilst the predictability of the vertical distance between seat and handlebars was weaker (R = 0.231, p < 0.001). These results have practical implications for children and parents, paediatric researchers and clinicians as well as bicycle manufacturers.