5.8 Office Ergonomics Self-Help Guidelines

Safety, Health, and Environmental Manual

These guidelines can help employees adjust their office furniture so they can work in greater comfort and better health. These standards are best practice guidelines. They deal with the relationship between average body size and the position of office furniture and computer equipment. However, these standards do not apply to every possible variation of body size. The size and shape of the employee’s torso and extremities affect the position and location of the furniture and equipment in an employee’s office. Sit-and-stand workstations are also available in the workplace. They too must be adjusted to the specific employees’ body types.

If you have questions about these guidelines, contact the Risk Management Division or your local area office.

5.8.1 Chair Seat Height

The seat height is the distance from the floor to the top side of the chair seat when the employee is sitting in his or her chair. Employees may use the following guidelines when adjusting chair height.

  • Sit in the chair in a comfortable, upright position.

  • Adjust the seat height up or down so your feet rest comfortably flat on the floor and your thighs are approximately parallel to the floor.

    • If your feet dangle slightly and the backs of your thighs press hard on the front of the seat, the chair is probably too high.

    • If your knees are elevated and your thighs do not touch the front of the seat, the chair is probably too low.

  • Consider the following if you like to lean back when working:

    • If your heels are lifted off the floor, consider lowering the seat height.

    • If your heels rise as you push with your feet to lean back, consider loosening the chair’s tilt tension.

  • If you like to sit forward, consider the following:

    • If you must tuck your feet in or place them out in front of you, consider raising the chair seat.

    • If you feel the chair seat tilts too much, consider tightening the chair’s tilt tension.

5.8.2 Chair Standards

When the chair has been adjusted, you may use a measuring tape to compare the adjustments with the recommended standards as outlined below.

  • Seat height should range from 16 to 21 inches (41 to 53 cm). This height refers to how high the chair seat should be with a person’s weight pressing on the cushions.

  • Seat depth for chairs with rectangular cushions or chairs made of hard materials should range from 15 to 17 inches (38 to 43 cm). Seat depth refers to the distance from the front edge to the back edge of the seat cushion. Seat depth can be greater if the front edge of the seat is soft or curved.

  • Measured across the middle of the seat, the seat width should be at least 18 inches (46 cm). Seat width refers to the side-to-side distance across the seat cushion.

  • Distance between armrests should be at least 18 inches (46 cm) measured between the inner edges of the armrests.

  • The backrest should be at least 12 inches (31 cm) wide in the lower-back area.

5.8.3 Work Surface

The proper height of the work surface is determined by the space between the employee’s legs and the work surface when the employee is seated. If the height of the employee’s work surface is adjustable, employees may use the following suggestions:

  • Sit on the chair and move it into normal working position next to your work surface. With your feet flat on the floor, adjust the height of the work surface so your knees do not bump the edge of the work surface, pencil drawer, or keyboard tray (when the tray is in working position, not in the storage position). The tops of your thighs should not touch the underside of the work surface.

  • When the chair is in normal position for working, your feet and knees should not bump against the back or upright of the work surface or the wall behind the work surface.

  • There should be enough clearance beneath the work surface for you to move freely when you swivel to grasp something within easy reach on the work surface. For example, your knees should not bump against storage drawers or brackets.

  • While you are sitting in an upright position, your forearms should rest comfortably on the work surface.

    • If the height of the work surface causes your shoulders to be raised up or hunched, consider lowering the work surface.

    • If you must slump or hunch over your work surface, consider raising the work surface so you can work in a comfortable, upright position.

If the height of the work surface is not adjustable, adjust the height of the chair to reach a comfortable work position. You may also use a footrest to bring your thighs approximately parallel to the floor.

Best Practice Standards

Check the work surface against the following recommended standards:

  • Knee space should measure at least 20 inches (51 cm) from side to side under the work surface, but 24 inches (61 cm) is preferred.

  • The underside of the work surface or keyboard tray should be higher than your knees. If you work at a desk with a work surface that cannot be raised or lowered, the clearance under the work surface should be at least 26 inches (67 cm).

  • From underneath the front edge of the work surface to the back wall supporting the work surface, there should be at least 12 inches (31 cm) front-to-back clearance at knee height. Taller people will need more clearance.

  • If you are using a standing workstation, stand on an antifatigue floor mat and wear proper footwear. A footrest to change your leg position may also be helpful.

5.8.4 Adjusting the Keyboard

  • Adjust the angle and height of the keyboard so the front of the keyboard is approximately at the same height as your elbows.

  • Forearms should be parallel to the floor.

  • Wrists should stay relatively straight or somewhere between straight and bent slightly upward.

  • Hands should not drop forward from the wrist.

5.8.5 Adjusting the Computer Monitor

  • After adjusting the keyboard, check the monitor location and angle.

  • Sit in a comfortable position, and look straight ahead to the horizon. The way a person sits (reclining, upright, and so on) affects the best position for the monitor. The entire monitor screen should be below your line of sight. If the monitor is too high, place it on the work surface (rather than on a processing unit).

  • If you have a standing workstation, elevate the monitor screen to eye level. Tilt the screen to approximately 20 degrees.

  • Some experts suggest that placing the center of the monitor about 30 degrees below the horizon will create the best angle for viewing the screen.

  • Adjust the monitor angle by placing a compact mirror against the center of the screen and tilting the monitor so you can see your eyes in the mirror while seated in a working position. (When doing so, be sure you do not rub the mirror directly across the screen and scratch the screen surface.)

  • If there is a bright light source behind your screen, such as a window, move your monitor or cover the light source with a shade.

  • If you look more often at documents than at the monitor screen while keying information, consider placing the document directly in front of you and the monitor slightly to the side. Do not place the monitor in a corner or other position that makes you twist your neck or body to see it while typing.

  • Some experts suggest that your monitor be at least 18 inches (46 cm) or more from your eyes.

  • The standards recommend that a capital letter on the screen should be at least 1/8 inch high (0.3 cm). If your eyes are more than 27 inches (69 cm) from the screen, the capital letter should be taller than 1/8 inch (0.3 cm).

5.8.6 Adjusting Your Mouse

If you have a mouse and use it only occasionally, you can put it at any convenient place on your work surface. If you use your mouse frequently, you may need to adjust its location.

  • When you are sitting in an upright position, your hand should rest comfortably on the mouse.

    • If the location of your mouse on the work surface causes your shoulder to be raised or your arm to be completely extended, you may need to adjust the location of your mouse. Adjustable mouse pads are available that slide out from under the work surface or attach to the keyboard tray. A wide keyboard tray will allow enough room for a mouse pad.

5.8.7 Adjustments throughout the Day

While working, employees should take a moment from time to time to evaluate their body posture and work movements. Generally, it is beneficial to move frequently and change position.

5.8.8 Other Suggestions

Employees should also consider the following questions and suggestions:

  • Are you striking the keyboard keys hard? Remember to soften your touch.

  • Are your shoulders raised or hunched? Relax and lower them. If the armrests of your chair are forcing your shoulders up, consider asking to have the armrests removed. If your work surface is forcing your shoulders up, consider asking to have the work surface lowered.

  • Do you keep your hands poised above the keyboard or telephone? Relax them; do not allow yourself to keep your hands frozen in one position.

  • Are you leaning against a sharply angled edge? Move back to relieve pressure on your forearms.

  • Are you leaning over to reach things at your workstation that could be placed closer? Do you often reach behind your body or above shoulder height to retrieve something that could be moved forward or down? Do your best to find an arrangement that keeps the materials you frequently use within convenient reach, about 20 inches (51 cm) away for a heavy object.

Finally, listen to your body. If you think you may be more comfortable adopting a different posture or way of working, experiment and find what is best for you.