I don't know what or how to measure for the right size wheelchair. How do I measure? What do I measure?
The first thing you need to do is take measurements of the person that will be using the wheelchair.
If you measure from top to bottom it will be easier.
Measure chest width and depth, hip width, seat to top of head, seat to occiput, seat to top of shoulder, seat to inferior angle of scapula, seat to elbow, seat to iliac crest, sacrum to popliteal fossa, knee to heel, and foot length.
Have the individual sitting on a chair or mat to make measuring easier.