A wheelchair that is too wide is hard to push and will not fit through doors; one that is too narrow rubs the hips and causes pressure sores. A seat that is too deep pushes the user into a slouch, and one that is too high makes the knees rise and the feet dangle. Five measurements taken with the person seated on a firm surface give a good starting point for every dimension.
How to measure
Sit the person upright on a firm chair, hips and knees at about 90 degrees, wearing the clothes and shoes they usually wear.
- Hip width: across the widest point of the hips or thighs.
- Thigh length: from the back of the buttocks to the back of the knee.
- Lower leg length: from the back of the knee to the bottom of the heel, with shoes on.
- Seat to armpit: vertical height from the seat to the armpit.
- Seat to elbow: with the upper arm hanging and the elbow bent at 90 degrees.
The rules
| Dimension | Rule |
|---|---|
| Seat width | hip width + 2 in (5 cm), 1 in on each side |
| Seat depth | thigh length - 2 in (5 cm), about two fingers behind the knee |
| Seat height | lower leg length + 2 in (5 cm) for footplate clearance |
| Back height | armpit height - 4 in (10 cm) for a mid back |
| Armrest height | elbow height + 1 in (2.5 cm) |
| Overall width | seat width + about 8 in (20 cm) for wheels and handrims |
Example
A person with hips 15 in wide and thighs 19 in long needs a 17 in wide, 17 in deep seat. A lower leg of 17 in gives a seat height of 19 in. The chair will be about 25 in wide overall, which passes a 32 in door easily.
Doors and homes
In the United States, the ADA requires a clear door width of at least 32 in. Older homes often have 28 to 30 in interior doors, which only narrow chairs pass. Offset hinges add about 2 in of clearance without widening the opening. Allow at least 1.5 in of clearance so hands on the rims do not hit the frame.
Active and transit chairs
Active users usually choose a lower back (below the shoulder blades) to free their arms, and a seat close to hip width for easy pushing. Transit chairs, pushed by a carer, have small rear wheels and are 4 to 6 in narrower overall. Electric chairs have their own dimensions; ask the supplier for the overall width.
Get a professional fitting
These rules give a first estimate. An occupational therapist or physiotherapist adjusts the cushion, seat angle, footplates and backrest to the person’s posture, skin risk and daily routine. For a person who spends many hours in the chair, the cushion matters as much as the frame.