Wheelchair Measuring & Sizing Guide

How to choose between a wheelchair and a transport chair, and how to measure for the correct size.

Last reviewed by A. Erickson, September 18, 2026.

This guide has three steps. First decide whether you need a self-propelled wheelchair or a transport chair. Then take your measurements. Then match them to a Strongback model. A tape measure and about ten minutes is all it takes.

Step 1: Wheelchair or Transport Chair, Which Is Right for You?

Transport chairs and lightweight wheelchairs look similar at first glance, but they are built for two different jobs. Getting this right matters more than any measurement, because it decides whether the user can move on their own.

Key Differences Between Wheelchairs and Transport Chairs

A self-propelled wheelchair has large rear wheels, 22 or 24 inches across the Strongback range, with a metal hand rim on the outside of each wheel. The user grips the rim and pushes themselves. A caregiver can push the chair as well, so a self-propelled wheelchair covers both modes.

A transport chair has small rear wheels and no hand rims. It moves only when someone else pushes it. Leaving out the large drive wheels makes the chair lighter, narrower and more compact when folded. The trade is that the user depends on a caregiver.

The quickest test is the rear wheel. If there is a metal ring on the outside of it, the chair is self-propelled. If there is not, it is a transport chair. Retail listings often use the phrase "transport wheelchair" for both types, so check the wheel rather than the product name.

Which Strongback Models Are Which

If you are not sure whether the user will want to push themselves or will always need assistance, an occupational therapist or physical therapist can help you decide. So can we.

For a longer comparison, read our blog post Differences Between a Transport Chair and a Lightweight Wheelchair.

Step 2: How to Measure

Get Into the Measuring Position First

Sit in a firm chair, not a couch or a recliner where the body sinks. Feet flat on the floor, knees at roughly a right angle, hips all the way back in the seat, no leaning and no slouching. Measure wearing the shoes that will be worn in the chair most often. A second person makes this much easier and much more accurate. If you are measuring alone, use a mirror or a phone camera to check your posture.

Measure Hip or Thigh Width, Which Sets Seat Width

Seat width is the single most important fit dimension on a wheelchair, and it is about the user's hips, not the user's weight.

• Have the person sit upright on a flat, firm surface.
• Position the tape horizontally across the widest point of the hips or thighs, whichever is wider. This is usually at the hip bones or the widest part of the thighs.
• Keep the tape level, neither tight nor loose.
• Add 1 to 2 inches (2.5 to 5.1 cm) for comfort and for small movements while seated.
• Add another 1 inch (2.5 cm) if bulky winter clothing will be worn in the chair.

A seat that is too wide costs the user their arm position and lets the trunk lean sideways, which is exactly what a supportive backrest is there to prevent. A seat that is too narrow pinches the hips and restricts circulation.

Measure Leg Length, Then Check It Against the Seat Depth

Seat depth is the distance from the front edge of the seat to the front face of the backrest. It is fixed on each Strongback model rather than adjustable, so this is a fit check rather than a number you choose.

• With the person still sitting, place the tape at the back of the hips, the rearmost part, and measure down to the back of the knee.
• That measurement needs to be at least 1 to 2 inches (2.5 to 5.1 cm) greater than the seat depth of the model you are looking at.

That gap is what keeps the front edge of the seat clear of the back of the knee. Without it the seat edge presses into the back of the knee and restricts circulation. If the gap is much larger than 2 inches, the thighs hang unsupported towards the front and more of the load goes onto the buttocks.

Measure Heel to Knee, Which Sets Seat Height

• Measure from the back of the heel to the back of the knee while seated.
• If the user will propel with their feet, use that measurement as the seat height so the feet reach the ground comfortably.
• If the user will propel with their arms, add 2 inches (5.1 cm) to allow footrest clearance.

Record the User's Weight and Height

• Weigh the user on an ordinary scale, or on a chair scale if they cannot stand.
• Note their height as well. The size chart in Step 3 uses both.
• Choose a chair rated comfortably above that weight rather than at it, so there is headroom for normal fluctuation.

Measure Your Doorways and Ramps

Overall width is the widest point of the chair, measured across the outside of the rear wheels. It is not the same as seat width, and it is the figure that decides whether the chair fits through your home.

• Open the door fully, to 90 degrees, and measure the narrowest clear opening. Bathroom doors are usually the tightest.
• Subtract 1 inch for hand clearance.
• Compare that against the Overall Width on the product page, not against the seat width.
• Check elevators and ramps the chair will have to use as well.

The Measurements at a Glance

Step 3: Match Your Measurements to a Strongback Model

Strongback Wheelchair Size Chart

Find the user's weight down the left and their height across the top. The cell gives the recommended size. A two-tone cell means either size fits, with the darker half being the wider seat, so choose on the user's hip measurement from Step 2 and on personal preference.

• S, 16 in seat
• M, 18 in seat
• L, 20 in seat
• HD, 22 in seat
• No Strongback option

"None" means no Strongback fits, because the user needs a seat wider than our 22 inch maximum. Call us and we will tell you honestly rather than sell you the wrong chair.

What the Sizes Mean

Size is a seat width decision. Self-propelled or transport is a separate decision about how the chair will be used, and both columns above share the same seat widths, so the chart applies either way.

S is not offered at 5'8" and over, because taller users need the longer seat depth and frame of the M. S, M and L are rated to 300 lb and so do not appear above that weight. The Heavy Duty is rated to 375 lb.

This chart is fit guidance, not a clinical seating assessment. If the user is between sizes, measure hip width as described in Step 2, or call us.

Frequently Asked Questions

How do I know if I am measuring correctly?

Sit in a firm chair, not a couch or recliner where you sink. Your feet should be flat on the floor, knees at roughly a right angle, hips all the way back in the seat. Do not lean forward or slouch. That is your measuring position. A second person helps, because it is hard to measure yourself accurately. If you are measuring alone, use a mirror or a phone camera to check your posture.

What if my measurements fall between two sizes?

Wheelchair seats come in whole inches, 16, 18, 20 and 22, so measurements often land between them. Round up, not down. A seat that is slightly too wide is easier to live with than one that is too narrow, which pinches the hips and limits circulation. If you are exactly in the middle, say 17 inches of hip width, the 18 inch seat is the right choice. The size chart shows two sizes in many cells for the same reason, and hip width is the measurement that decides between them.

Why does the size chart use weight and height rather than hip width?

Weight and height are the two numbers most people already know, so the chart gets you to one or two candidate sizes without a tape measure. Hip width is what settles it. Where a cell offers two sizes, measure hip width as described in Step 2 and pick the seat that matches. If the two disagree, trust the hip measurement.

Why does seat width matter more than seat depth?

Seat width decides whether the chair fits the body. Seat depth decides how the thighs are supported. A seat that is too wide creates the bigger problem: the trunk drifts sideways looking for a stable position, which undoes whatever back support the chair provides. A slightly wrong depth is uncomfortable. A seat that is too wide is dysfunctional. Check both, but get seat width right first.

Should I measure with or without shoes?

Measure with the shoes that will be worn in the chair most often. If that is slippers or bare feet, measure in slippers or bare feet. The goal is the position the user will actually sit in. If they switch between shoes and no shoes regularly, measure both ways, because the right seat height can differ.

What if I cannot get to a retailer to try chairs?

Measure carefully using this guide, then call us at +1 757 349 7790. Describe your measurements, your weight, the surfaces you transfer to such as bed, car seat, toilet and shower bench, and what the chair will be used for most. We will help you narrow it down, and we can usually settle sizing questions over the phone. If you order from this website and the fit is not right, you have 30 days from delivery to request a return authorization. See Warranty and Easy Returns for the full terms.

How do I know if a wheelchair's seat height matches my transfer surface?

A level transfer, where the wheelchair seat and the surface you are transferring to sit at the same height, is far easier than an uphill or downhill one. Measure the height of your bed, car seat, toilet or shower bench. If your transfer surfaces are unusually high or low, tell us, because seat height is one of the first things to discuss.

Do I need a physical therapist or occupational therapist to measure?

Not necessarily. If the user has good posture, can sit upright unaided and understands the measurements, you can do this yourself or with a friend's help. If there is limited trunk control, pain while sitting or balance problems, or if you are measuring for someone else with mobility challenges, an occupational therapist or physical therapist will give you more precise measurements and catch things that are easy to miss. That is especially useful for transfer-focused chairs such as the Comfort Flip and the Excursion, where a therapist can measure against the user's own transfer surfaces.

What if my weight is close to the chair's weight capacity?

Choose a chair rated above your weight, not at it. If you weigh 240 lb, do not choose a chair rated to 250 lb, because that leaves no margin. The Strongback Comfort, Comfort Flip, ErgoSteel and Excursion are rated to 300 lb, and the Strongback Heavy Duty is rated to 375 lb. Pick the one that sits comfortably above your weight, with headroom for normal fluctuation over time.

How do I check seat depth correctly?

Seat depth is fixed on each Strongback model, so there is no number to calculate. What you do is check that the model fits you. Get into the measuring position, measure from the back of your hips to the back of your knee, and write that number down. Your measurement needs to be 1 to 2 inches greater than the model's seat depth, which leaves the seat edge clear of the back of your knee. For example, an 18 inch seat depth wants a hip to knee measurement of 19 inches or more. If your measurement is smaller than the seat depth, the seat will press into the back of your knee and that model is not the right one. Ask us if you are close either way.

Is seat width the same as the chair's overall width?

No. Seat width is measured between the inside faces of the armrests and is about the user's body. Overall width is the widest point of the whole chair, measured across the outside of the rear wheels, and it is the figure that decides whether the chair fits through a doorway. Always check overall width against your narrowest opening before ordering.

Still Not Sure Which Size to Order?

You can also find a Strongback retailer near you and sit in the chair before you decide.