A child's wheelchair is sized according to height and weight. The seat width is also important, as it needs to be wide enough to support the child's hips and thighs. Most children's wheelchairs have adjustable seat heights and depths so that they can be customized to fit each individual child. The armrests should also be adjustable so that the child can comfortably position them. Finally, the footrests need to be the right size and shape to support the child's feet and legs.