Chair Angle Calculator — Ergonomic Dimensions

For a standard 750mm dining table, seat height should be 430-460mm for most adults. This is based on the popliteal height (back of knee to floor), which is approximately 25% of body height, plus a small shoe-sole allowance. Too high and feet dangle; too low and thighs are angled upward, which is uncomfortable for eating.

For a dining chair, the back should be 93-97 degrees from the seat (just past vertical). For a reading or relaxed chair, 100-105 degrees. For a lounge or recliner, 110-115 degrees. The seat should also tilt back slightly (3-5 degrees for dining, up to 12 degrees for a lounge chair) to keep the sitter from sliding forward.

Typically 3-7 degrees outward. Dining chairs use 3-5 degrees for a clean look while maintaining stability. Lounge chairs benefit from 7-10 degrees for a wider, more stable base. The splay must be compound — outward both to the front/back and to the sides. A wider splay makes the chair more tip-resistant.

The seat depth should be about 50mm less than the buttock-to-popliteal length, to avoid pressing into the back of the knees. For an average adult (175cm tall), this is about 400mm. Too deep and the sitter cannot use the backrest; too shallow and there is insufficient thigh support.

Armrests should be about 200-250mm above the seat surface. This allows the forearms to rest naturally with shoulders relaxed. Too high forces the shoulders up; too low causes the user to lean sideways. For dining chairs, armrests must clear under the table apron — typically 630mm from the floor.