Office Ergonomics Reference Guide

Section 3

CHAIRS

The chair must fit the user, as well as suit the tasks to be performed.

One style of chair may not suit every user.

The chair should provide support and stability to the user and allow movement through multiple positions.

What Makes a Chair Ergonomic? 

A chair is only “ergonomic” if the user can adjust it to fit their own personal dimensions. 

In order to do this, the following parts of a chair need to be adjustable:

Icon showing the seat pan of an office chair
Seat pan

(height and depth)

Icon showing the adjustable backrest of an office chair
Backrest

(height and angle)

Icon illustrating the lumbar support in the backrest of an office chair
Lumbar Support

(height and depth)

Icon showing adjustable armrests on an office chair
Armrests

(height, width and ability to rotate)

Illustration showing the various parts of an office chair including the backrest, lumbar support, arm rest, seat pan, and casters.

Seated Neutral Posture in an Adjustable Chair

 

It is important that the user understands the proper positioning of these features to allow for optimal support and to maintain neutral sitting postures.

Each of these features is discussed in detail below:

Seat Pan Depth

Having a seat pan that is the correct size is an essential feature.

If the seat is too deep, it will create a pressure point on the back of the legs. This will not only reduce blood flow and nerve supply but also cause the user to slide forward, reducing the effectiveness of the lumbar support.

The simplest way to determine if the seat pan is too deep is to perform the “fist” test.

An illustration showing how to conduct a "fit test"to determine if a chair seat pan is deep enough for the user

The “Fist” Test

Sitting properly in the chair the user should be able to place their fist (maximum) or two fingers (minimum) between the front edge of the seat pan and the back of their legs.

If this cannot be achieved, the seat pan depth is either too deep (less than two fingers), or too short (more than fist):

• If the chair has seat pan depth adjustability, make the required adjustments.

• If the seat pan cannot be adjusted, and is too large for the user, then the seat pan or chair must be replaced with one that is the correct size for the user.

The front edge of the seat pan should be rounded to avoid pressure points.

Illustration showing a proper seat pan with a well-rounded front edge as well as a poorly shaped seat pan with a square front edge


Seat Pan Width

Ensure that the correct seat pan size is provided to the user based on their physical size and dimensions.

Chairs can be provided in various sizes to accommodate different users.

Illustration of the front and top view of an office chair showing the adjustable armrests to accomodate different sizes of users

Adjustable Armrests

The width can be further accommodated by making changes to the armrests (rotated or adjusted in width from the base).

If armrests have width adjustability, position them to fit the user.
(See Armrests below).


Seat Height

The seat height is dependent on the physical size and dimensions of the user.

The user’s working height (on the desk, height adjustable workstation, or on a height adjustable keyboard tray) also dictates the height at which the seat is positioned.

The seat height should allow the user to:

• Sit with their feet resting comfortably on the floor or a footrest.

• Work with their upper extremities in neutral postures.

• Make easy adjustments to allow for postural variation and different footwear.

There are three simple ways to ensure your seat is at the correct height:

Illustration of person sitting at a workstation using an adjustable keyboard tray

1. Keyboard on keyboard tray

Illustration of a person sitting at a workstation with the keyboard positioned on the workstation at the correct height

2. Keyboard on workstation (no footrest)

3. Keyboard on workstation utilizing footrest


Seat Angle

The seat pan angle should:

• Be adjustable and independent of the backrest adjustments.

• Allow the user to maintain support of their feet on the floor or footrest.

Illustration showing the correct and incorrect angles of the seat pan on an office chair

If your seat cannot be lowered or raised to the proper height, then the cylinder may be replaced with one that allows for the proper adjustments.

Illustration of an office chair showing a detail of the chair cylinder in various sizes

Adjustable Cylinder

Backrest Height

The backrest height should be:

• High enough to support the users back, shoulders, and neck.

Illustration showing the ideal height of a backrest versus backrests that are positioned too high or too low


Lumbar Support

The lumbar support helps maintain the natural curvature of the spine.
The lumbar support should:

• Be height adjustable in order to accommodate the user.

• Be shaped to accommodate the user.

• Not cause any localized pressure points.

Illustration showing the location of the lumbar support on an office chair


Backrest Width

The backrest should:

• Be wide enough to provide adequate support to the user’s back.

• Not cause any localized pressure points.

Illustration showing the backrest width of an office chair


Backrest Angle

The backrest angle should:

• Be positioned 90 to 110 degrees depending on personal preference.  

• Ensure the lumbar support is positioned in the curvature of the user’s lower back.

Illustration showing the optimum range of angle for the backrest of an office chair

The armrests on a chair should:

• Support the arms.

• Allow access to the workstation.

• Distribute forces evenly.

• Allow the user to sit in a variety of postures.


Armrest Height

The armrest height should:

• Be adjustable and support the user’s forearms and/or elbows.

• Allow users to maintain neutral posture. 

• Should not cause the user to elevate or drop the shoulders in order to rest the arms.

Illustration showing the correct and incorrect heights for office chair armrests


Armrest Length, Width, and Positioning

The length, width, and positioning of the armrests should:

• Allow users to maintain a neutral posture.

• Support the user’s forearms and not cause excess contact stress.

• Not impede the user’s ability to access the workstation.

• Allow for width adjustability.

• Pivot or rotate to allow chair to be positioned as close as possible to the workstation (shown below).

• Allow the user to enter and exit the chair easily.

Illustration showing the length, width and position of the armrests on an office chair

The casters on the chair should be appropriate to the type of flooring.

Illustration showing hard casters (wheels) on an office chair

Hard Casters
  Lower rolling resistance
  Recommended for soft surfaces (carpeted floors)

Illustration showing soft casters from an office chair

Soft Casters
•  Higher rolling resistance
•  Recommended for hard-surface floors (tile, laminate)

Important Considerations

Icon for bottle of lubricant

Preventative maintenance (e.g. cleaning and lubricating) is suggested to ensure ease of operation.

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