Measurement Guide
7 Measurements That
Determine Your Fit
A wheelchair that doesn’t fit your body causes pressure injuries, shoulder damage, and inefficient propulsion. Here’s how to take the measurements that determine fit — correctly — before you build your chair.
What you need
- A soft measuring tape (cloth or flexible plastic)
- A firm, flat surface to sit on (not a couch or soft chair)
- The shoes or footwear you typically wear in your chair
- A helper — most of these are easier with a second person
- A notepad or the PDF worksheet below
- Your current wheelchair, if you have one (serial number and spec sheet help)
Don’t stress if you can’t get everything yourself. Daryl can guide you through measurements during a free fit consult. The more you have ready, the more specific the recommendations can be — but missing a measurement is not a reason to delay.
The 7 measurements
Seat Width — Hip Width + Clearance
What it is
The widest point of your hips or thighs in a seated position.
Why it matters
Determines the internal frame width. Too wide → inefficient propulsion arc, shoulder problems. Too narrow → pressure points at the greater trochanters and outer thighs.
How to measure
Sit on a firm, flat surface. Measure across the widest point of your hips/thighs with a soft tape measure. Add 0.5–1 inch for clearance. This is your target seat width.
Common mistake
Measuring standing hip width. Seated width is different — often wider — because soft tissue spreads when you sit. Always measure seated.
Seat Depth — Popliteal to Back of Buttock
What it is
The distance from the back of your buttock to the crease behind your knee.
Why it matters
Determines how far back the seat extends under your thighs. Too deep cuts off circulation behind the knee and causes skin breakdown. Too shallow shifts weight onto your sitting bones and tips the pelvis forward.
How to measure
Sit on a firm, flat surface with your back against a wall. Measure from the wall to the crease behind your knee. Subtract 1–2 inches for clearance. That's your seat depth.
Common mistake
Forgetting the clearance subtraction. A seat depth equal to your full measurement will press against the back of the knee. The 1–2 inch clearance is not optional.
Back Height
What it is
The height from the seat surface to the top of your back support.
Why it matters
Back height determines how much trunk support you get and how much propulsion clearance you have. Too high restricts shoulder movement during propulsion; too low provides insufficient trunk support.
How to measure
Sit on a firm, flat surface. For active users, the back height is typically 1–2 inches below the bottom tip of your shoulder blade — low enough that your arm can swing freely through a full push stroke. For users who need more trunk support, measure to your shoulder height.
Common mistake
Setting back height to shoulder height for active users. A lower back (stopping below the shoulder blade) allows your arm to move freely through its full range — this protects your shoulder over time.
Lower Leg Length — Seat to Heel
What it is
The distance from the back of the knee to the bottom of the heel.
Why it matters
Determines footrest height. If the footrests are too high, your thighs are lifted off the seat, which puts too much pressure on your sitting bones. If too low, your feet dangle and your thighs bear no weight — also bad.
How to measure
Sit on a firm surface with your knee bent at 90 degrees. Measure from the crease behind your knee to the bottom of your heel. Note: measure in the shoes or footwear you plan to use in the chair.
Common mistake
Not measuring in footwear. A 1-inch heel changes the effective lower leg length and therefore the footrest height needed. Always include shoes in the measurement.
Trunk Width
What it is
The width of your torso at the widest point of your ribcage, measured seated.
Why it matters
Relevant for lateral trunk supports and back width. If you have significant trunk asymmetry, this helps determine the back support configuration.
How to measure
Sit upright. Measure the width of your ribcage at the widest point. Compare to your hip width — in most users, hip width determines seat width, but trunk width informs back support configuration.
Common mistake
Skipping this measurement if you have postural asymmetry. Obliquity and rotation affect how trunk width translates to support needs. Don't estimate — measure.
Hip Width — Widest Point
What it is
The widest point of your hips and upper thighs, measured seated.
Why it matters
This is typically the primary measurement for seat width determination. Some users are wider at the hips than the thighs — this is the relevant number for seat width.
How to measure
Sit on a firm surface. Measure the widest point of your hips and outer thighs. Compare to measurement #1. Use whichever is wider as the basis for seat width + clearance.
Common mistake
Using the narrower of two measurements. Always use the widest point. A chair that's slightly wide is manageable; a chair that's too narrow causes pressure injuries.
Body Weight
What it is
Your current body weight, in pounds.
Why it matters
Determines frame weight capacity and cushion selection. Every frame has a published weight limit. Weight also informs cushion type, pressure injury risk, and seat support requirements.
How to measure
Current body weight in pounds. If your weight fluctuates significantly (10+ lbs regularly), note the range. Use your higher weight as the planning figure for capacity decisions.
Common mistake
Using an outdated weight. If you haven't weighed yourself recently, do so before you order. A 30-pound underestimate affects both frame selection and cushion specification.
Have ready for a consult
- All 7 measurements above, written down
- Your diagnosis and a brief functional history (how long you’ve been using a wheelchair, any recent changes)
- Any history of pressure injuries, skin breakdown, or wounds
- Your current chair make, model, and serial number if applicable
- Any existing seating evaluations, PT/OT notes, or prescription documentation
- Your insurance information — even though chairs are cash-pay, Daryl may reference it for chair ordering context
Ready?
Build your chair.
Free guidance whenever you want it.
Configure any chair online with live weight, width, and price. Want a hand getting the measurements and options right? A free fit consult with Daryl Bullard is yours for the asking.