Office chair adjustments that matter
An office chair supports the back, legs, and arms only when its adjustments match the user. Key settings include seat height, backrest recline, lumbar support, and armrest position. This article explains what each adjustment does and how to check it against guidance from OSHA, CCOHS, and HSE.
Why chair adjustments matter
A well-designed and appropriately adjusted chair is essential for a safe computer workstation. The OSHA computer workstation eTool lists goals such as the top of the monitor at or just below eye level, shoulders relaxed, and feet flat on the floor, all of which depend on chair positioning.
No single posture fits everyone. The Cornell University Ergonomics Web describes ergonomics as human-centered design, meaning that adjustments should match the individual's body dimensions and tasks.
A chair becomes ergonomic only when it suits the user, the workstation layout, and the tasks performed. For example, a chair that is too high or has armrests too far apart can create discomfort.
Backrest and lumbar support
The backrest should conform to the natural curvature of the spine and provide adequate lumbar support. The OSHA chair guidance states that the backrest should recline at least 15 degrees from vertical and lock in place or have adjustable tension to support the lower back.
A lumbar support that is height adjustable can be placed in the small of the back. If a chair lacks built-in lumbar support, a rolled towel or removable cushion can serve temporarily.
The backrest should also be adjustable forward and backward. This allows shorter users to sit with their backs supported without the seat edge pressing on their knees, and taller users to have full thigh support.
Seat height and depth
Seat height sets the foundation for posture. According to the CCOHS ergonomic chair guidance, an optimal seat height is about one-quarter of the user's body height. The user should be able to sit with feet flat on the floor or on a footrest without pressure under the thighs.
Seat depth is equally important. The HSE good posture guide recommends leaving a gap of 2 to 3 cm between the front edge of the seat and the back of the knee.
When the seat is too high, users may slide forward and lose back support. A footrest can help when the chair cannot be lowered enough to align with the desk.
Armrests, base, and overall setup
Armrests, if present, should be soft, allow shoulders to relax, and keep elbows close to the body. They should be adjustable in height and width, and removable if they prevent moving close to the desk.
The chair base should have five legs with casters that suit the floor type. A five-point base provides stability, and casters allow easy movement. Controls should be operable from a seated position.
After adjusting the chair, the rest of the workstation must align. For instance, the keyboard should be at elbow height and the screen directly in front. For help choosing a chair with the right adjustments, the gaming and office chair directory lists models by fit and style.
| Adjustment | What to check |
|---|---|
| Seat height | Feet flat on floor, thighs supported without pressure |
| Backrest height | Lumbar support fits the small of the back |
| Backrest recline | At least 15 degrees from vertical, locked or tensioned |
| Seat depth | Gap of 2-3 cm between seat front and back of knee |
| Armrests | Elbows close to body, shoulders relaxed, adjustable width |
| Base | Five-point base with casters matching floor type |
Frequently asked questions
How often should a chair be readjusted?
A chair should be adjusted whenever a new user takes the seat or when the user changes tasks. Regular small adjustments can also help reduce fatigue, but there is no fixed schedule.
What if the chair lacks some adjustments like lumbar support?
A rolled towel or removable cushion can provide temporary lumbar support. A footrest can compensate if the seat is too high. If the chair cannot be adjusted to fit, consider a different chair.
Should armrests always be used?
Armrests help when they allow elbows to stay close and shoulders relaxed. If they prevent moving close to the desk or create pressure points, they should be adjusted, removed, or replaced.