Measure from the most posterior point of the body to the inside of the knee when in the seated position, then subtract approx 5cm. This gap can be increased to give more leg overhang if more room is needed for a hand to lift the leg.
This is the distance from the seat base to the top of the wheelchair back. This will depend on how much upper back support is needed. This will affect the freedom for the upper body to rotate.
Front Seat to Floor
Measure the leg from the back of the knee to the sole of the foot. Then subtract the thickness of the cushion when it is compressed. Then add 6-8cm for clearance between the footrest and floor. If the wheelchair is to be foot propelled do not add the 6-8cm.
Rear Seat to Floor
This is the measurement from the ground to the rear seat edge. Relative to the front seat-to-floor dimension, this determines the rearward slop of the wheelchair seat.
The wheelchair user should be measured at the widest point between the knee and hip, plus 2-3cm to allow enough room to move. Consideration must be given to the type of clothing likely to be worn.