“I don’t like my chair.” I hear it all the time. My next logical question as an ergonomics professional is “why?” Many times, I hear that comfort is the biggest complaint about an office chair. Subsequently, this is related to some aspect of the chair seemingly not fitting the user. I have found that the majority of chair users do not know that their chair has this essential adjustable feature that can change their opinion about their chair. This magical feature is seat pan depth adjustment.

Imagine sitting at a basketball game in the bleachers. How would you describe the seating? It’s hard, not adjustable, not supportive, not made for you, not comfortable. So how do you compare your office chair to that of a bleacher at a basketball game? That office chair isn’t looking so bad after all.

Office chairs come in all shapes and sizes with a wide array of features. Adjustable arm rests, adjustable seat height, seat back tilt tension, lumbar support, and seat pan depth adjustment are among the most commonly found features on office chairs. Of all these features, seat pan depth is the one that is hidden and often overlooked and often unknown. If I had a dollar for every time someone said “I didn’t know that my chair did that” . . .

I argue that seat pan depth is one of the most important adjustable features of an office chair that enables improved ergonomics and, in turn, comfort. The effect that is has on the back and how we are supported is pretty cool. Making this simple adjustment to an office chair during an office ergonomics observation flips the user from “I don’t like my chair” to “wow, it feels like a completely new chair” almost instantly.

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Why is seat pan depth so magical?

Back to the bleacher example. A bleacher is about 12 inches wide. This induces increased contact stress on the fanny which is uncomfortable. Portable seat cushions are great for improving this (see example at Amazon). The support provided by the bleacher seat does not properly support the legs and hips which can result in increased muscle activity of the supporting muscles of the back (this is the ergonomic risk factor of static loading).

The back that is not supported by the hips and legs can result in fatigue and back pain. This is the root of why people don’t like their chairs when they are not properly supported.  This is also why stability ball chairs are frowned upon in the office seating world. We as humans, come in all different shapes and sizes. A shorter stature person will have shorter legs where a taller person will have longer legs.

People generally think that seat height adjustment is all that is needed to accommodate short and tall populations. It’s only one of the essential adjustments required to properly fit an office chair to the user. The adjustment of seat pan depth is what enables the chair to adapt to various statures by lengthening or shortening the seat pan to provide leg support.

How to properly set seat pan depth

To adjust your chair’s seat pan depth, follow these steps:

1. Sit all the way back in your chair so your back is against the backrest.
2. Check the space between the back of your knees and the front edge of the seat.
   • The ideal space is about two inches, or the width of two fingers.
   • If the chair is touching the back of your knees or there’s more than a two-inch gap, adjust the seat pan depth so that it’s just right.

Making the adjustment on your chair

This varies by chair make and model. Find the instruction manual or a chair settings video for your specific chair. There is usually a make and model label under the seat pan of your chair. If you find that your chair does not have this adjustable feature the seat pan is hitting you in the back of the knees, you can use an aftermarket lumbar support or simply use a pillow. This will push you forward in the seat enabling proper upper leg support.

When you have a properly adjusted chair and it fits you, you are not only going to be more comfortable, you will have less fatigue, have higher productivity, and your risk for injury decreases.

Making this adjustment on office chairs has resulted in many happy people. I wish that everyone knew about it – but what else don’t people know about their chairs or office set up? Consider enrolling in my short course “Beyond the Office: Digital Ergonomics for the Every Day Person” where you’ll learn more great content like this. You’ll learn even more about your seating, digital displays, mouse, keyboard, and desk types and their uses.

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