Ergonomics and Product Interactions

This page uses the example of a chair to introduce you to concepts of ergonomics


Ergonomics is about ensuring a good fit between people and the things they interact with to increase the safety, comfort and performance of a product or an environment. It is an important part of research in the product development process and should be considered early on in the design process so as not to ignore the needs to the consumer.

Ergonomics uses anthropometrical data to determine the optimum size, shape and form of a product, and make it easier for people to use, helping you to identify which user characteristics you should take into account during your design process. This is important when you consider how much individuals vary in terms of:

  • body size

  • body shape

  • strength

  • mobility

  • sensory sensitivity

  • working postures

  • manual handling

  • repetitive movements

  • musculoskeletal disorders

  • workplace layout and environment

  • and more!

When designing furniture there are standard dimensions and design guidelines for many common types of furniture but it is best to consider these standards as starting points - if you are building custom furniture, design to the target user.

Look at furniture around you, and furniture you admire, measure yourself and those around you and decide what is most comfortable for you and your target end user and go from there. The workshop is currently working on an adjustable chair design to demonstrate ergonomic measurements that can be tailored to your requirements.

Example: Chair Design Guidelines

  1. The occupant should be able to sit in and get up from the chair without difficulty.

  2. The feet should rest flat on the floor without the knees projecting above the upper leg.

  3. Armrests should support the forearms without raising the shoulders.

  4. Half armrests enable the chair to be drawn up close to a table.

  5. The depth of the seat should allow clearance from the front edge of the seat to the back of the occupant’s leg.

  6. A seat that is too deep will press against the back of the legs forcing the occupant to slouch forward.

  7. A seat that is too shallow may be unstable and feel precarious.

  8. The width of the seat often tapers from the front to the rear to allow clearance for legs and clothes in front while allowing elbow room in back.

  9. For relaxed seating, the seat should slant slightly toward the back (about 8-15°) to keep the occupant from slipping out of the chair.

  10. A dining chair seat should slant slightly towards the back (about 2-5°)

  11. An office desk or typist’s chair often has a flat seat to facilitate leaning forward.

  12. The chair back angle should increase accordingly to the seat tilt.

  13. The seat back should support the lumbar region without being so high as to interfere with the shoulder blades. - Note that this guideline is often ignored for formal “high-backed” dining chairs.

  14. The lower portion of the seat back should curve out or be left open to allow room for the buttocks.

Chair Dimensions For Average-Sized Adults

The following dimensions apply to chairs designed for average-sized adults sitting in an upright or alert posture.

Design element

Traditional measurement

seat width

405 - 508 mm

seat depth

380 - 460 mm

seat height from floor

405 - 460 mm

slope of seat - front to rear

5 - 8 degrees

armrest height above seat

178 - 203 mm

armrest length

203 mm at minimum

set back of armrest from front

50 - 76 mm

seat back height

304 -405 mm above seat

seat back recline angle

0 - 5 degrees (formal); 01 - 15 degrees (casual)

Dining Chair

The seat height averages 406 - 432 mm, seat width averages about 380 - 395 mm in back and 457 mm in front, and average seat depth is 406 - 419 mm. If armrests are used, they should be 178 to 229 mm above the seat but able to fit under the table apron. The average width between armrests at the front of the chair is approximately 483 mm. The seat is usually level or has a maximum front to back slope of about 25 mm. The seat back is reclined no more than 5 degrees and ranges in height from 305 - 508 mm above the seat (or higher in very formal chairs).

Easy Chair

Should provide a more relaxed, reclining position than a dining chair – seat height is lower (about 406 mm) with allowance made for compression of seat cushion. The seat is angled backwards about 10 degrees with a seat to back angle of 95 - 120 degrees. For maximum comfort, the seat back should be no more than 356 - 406 mm above the seat. Armrests are recommended for easy in/out and they average 127 - 203 mm in height and 50 - 101 mm in width.

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