Seat depth determines how much of the user's thighs are supported by the seat. A seat that is too deep may prevent a shorter user from sitting fully back against the backrest, while a seat that is too shallow may provide insufficient thigh support for a taller user.
The appropriate seat depth depends on the user's body proportions as well as the chair's backrest and lumbar-support design. Some ergonomic chairs provide adjustable seat depth to accommodate a wider range of users.
Seat depth should be considered together with seat height rather than evaluated in isolation.
