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If there was ever a learning curve for me in my 32 years of experience with power wheelchairs, it was in the term “seat-to-floor height.”

See, for around the first 15 years of my power wheelchair use, seat-to-floor heights effectively didn't exist. Sure, every power wheelchair had a literal seat-to-floor height – that is, the distance from the front edge of the seat to the ground – but it was fixed, non-variable by model. If you purchased an Abec power wheelchair, you got whatever single seat-to-floor height it featured, and the same went for the E&J and Invacare models, as well – there was no choice. And, as users, no matter if our new power wheelchair came with a 17” seat-to-floor height, or one that was 21”, we simply adapted to whatever seat height at which we sat.

However, times changed, and user-specified seat-to-floor heights came into season, namely due to two trends: A shift toward “power base” designs in power wheelchairs, and the popularity of highly-adjustable manual wheelchairs. Conventional power wheelchairs featured the seat as part of the frame, so because the seat upholstery fastened to the side frames, there was no way to adjust the seat-to-floor height. However, power base designs – where the seat was separate, and sat atop the power base – allowed the seat to be raised and lowered within a range. Then, with manual wheelchair users discovering that achieving a tailored seat-to-floor height through adjustment could make many aspects of life easier – namely, transfers and table access – user-specific seat-to-floor heights began gaining popularity across the range of mobility products, moving from manual wheelchairs to power wheelchairs.

Today, seat-to-floor heights are arguably an obsession among consumers, clinicians, and manufacturers, where seat-to-floor heights are specified to the thousandths of an inch, and power wheelchairs are sometimes chosen by consumers and clinicians almost exclusively based on seat-to floor height potentials.

However, how consequential are seat-to-floor heights, how are they determined, and can one ever take them too literally?

Seat-to-Floor Height Factors
For starters, seat-to-floor height is a critical factor in power wheelchair use, dictating the height at which one sits – and, as a result, how one accesses one's environment. An ideal seat-to-floor height allows easier transfers to commodes and beds alike, and can enhance aspects like windshield visibility when driving a van from a power wheelchair, or allows one to tuck one's knees under a desk.

However, as one can imagine, there's vast subjectivity to an ideal seat-to-floor height for any one person or environment. One's bed is usually taller than one's commode, and one's desk may be a different height than one's dinning table, so compromises sometimes have to made in selecting a seat-to-floor height that fits in all of one's environments. What's more, a tall person may require a higher seat-to-floor height than a shorter person – specifically so one's long legrests clear the ground – so there's physical subjectivity to an ideal seat-to-floor height, as well. (And, let us not overlook the fact that a seat cushion increases seat-to-floor height by its compressed thickness, where a 2” cushion seats one lower than a 4” cushion.)

The goal, then, in selecting a seat-to-floor height is in balancing one's overall environmental and physical needs, and finding the number that best serves as an “average” toward overall functionality.

When a power wheelchair's seat-to-floor height is specified on an order form, it's measured from the bare seat pan to the ground, not including the cushion (the exception is captain's type seating that incorporates padding and upholstery).

Adult rehab power wheelchair seat-to-floor heights generally range from 16.625” to 22”, varying by model and seating. For example, on a particular power base, the lowest seat-to-floor height with a non-powered rehab seat might allow from 16.625” to 20” based on adjustable mounting towers, but a power lift-and-tilt may start at an 18” seat-to-floor height based on space needed for its mechanisms. Therefore, while most power bases and seating today offer adjustable seat-to-floor height ranges, it varies by model and seating. Again, when mixing components, there's often not an ideal, but a balance, where one's seating, power base, and stature must be balanced to a functional seat-to-floor height.

Then, how does one establish a seat-to-floor height that will best balance overall functionality? The answer is, by studying one's uses and environments:

How tall are all of the transfer surfaces that one encounters daily?

At what height does one need to sit to appropriately drive one's van?

Is there any extraordinary environmental access issue that needs especial consideration, such as fitting under a work station?

Again, not all environmental factors are at the same height – one can't say that a single seat-to-floor height measurement ideally applies to all factors.  However, if one's raised commode is 19” high, one's bed is 24” high, and one finds that an 18” seat-to-floor height would be ideal for driving, a 20” total seat-to-floor height (which would be a 17” pan height plus 3” of compressed cushion height) may prove the ideal “average” of all three surfaces, placing you in a realistic position to access them.

To the contrary, a 16.625” or 22” seat-to-floor pan height would place one outside of all of the previously-described environmental “sweet spots,” so it wouldn't make sense to go below or above one's environmental needs. Therefore, in determining one's meaningful seat-to-floor height, a simple mathematical equation of adding your environmental surface heights, then dividing by their quantity (as in, commode + bed + van, divided by 3 = average seat-to-floor height, then factoring in a cushion), makes for a practical formula to determine a successful seat-to-floor height.

Avoiding Extremes
While some consumers require an ultra-low or super-tall seat-to-floor height for environmental or physical reasons, it's important not to assume that “extremes” are better for a user without full considerations. For example, there have been clinicians who believe that the lower the seat-to-floor height, the better. However, while a sub-17” seat-to-floor height may be fine for some transfers and environments, it may not be ideal for most. For example, I use a 19” seat-to-floor height, with an additional 3” of compressed cushion, and due to my stature and environment, it serves me ideally. However, if I were seated at an ultra-low 16.625”, I would certainly be very uncomfortable at my kitchen table and desk, couldn't reach into my sink, and transferring onto my 24”-high bed would be a major uphill climb – so shorter doesn't always mean better.

Similarly, some consumers assume that a taller seat-to-floor height is better, allowing them to reach high objects and look those who are standing more closely in the eyes. Yet, a super-tall seat-to-floor height can make fitting under desks and tables impossible, as well as make lower-level transfers very difficult. Therefore, taller is rarely better.

In these ways, rather, than automatically presuming that an extreme seat-to-floor height – shorter or taller – is an ideal, clinicians and consumers should truly consider one's individual needs, then select a fitting measurement.

Nitpicking Numbers
Another pitfall of seat-to-floor heights to avoid is getting too concerned with decimal differences. A 17.375” versus a 17.475” seat-to-floor height truly will not impact one's functionality. Yet, clinicians and consumers have been known to select one seating system over another due to one-tenth of an inch difference in seat-to-floor height (and some will even use a hundredth or thousandth of an inch as a deciding factor!). Literally, one's pants thickness or wheelchair tire wear can vary by one-tenth of an inch, so picking one seat over another based on one-tenth of an inch is really a moot point (and, simply going from flat-free to pneumatic tires increases a power wheelchair's seat to floor height by three-eighths of an inch – so fretting over one-tenth of an inch in seat-to-floor height proves entirely pointless). One-half inch in seat-to-floor height may make a difference; however, nitpicking numbers to the tenth, hundredth, or thousandth of an inch serves no purpose.

The Right Height
Indeed, finding the right seat-to-floor height of a power wheelchair in relation to a specific individual's needs really comes down to fundamental points:

-Rehab seat-to-floor heights on order forms are measured from the ground to the bare seat pan.

-The functional seat-to-floor height includes the cushion compressed under the user's weight (as in, a 17” seat-to-floor height plus a 3” compressed cushion equals a 20” functional seat-to-floor height).

-Measuring vital transfer heights and other environmental access points, like desk heights, then averaging their heights can prove a practical method to determine an optimized all-around seat-to-floor height.

-Avoid extremely low or extremely tall seat-to-floor heights unless necessity dictates them.

-Don't dwell on measurements within a tenth, hundredth, or thousandth of as inch of each other, as they become truly inconsequential.

Following these fundamentals will place you in the sweet spot of sitting, where your transfers won't feel like your plunging into the Grand Canyon or climbing Mount Everest.

Published 9/09, Copyright 2009,