Every chair listing describes itself as ergonomic and supportive, which tells you nothing about whether it will fit you. The figures that decide that are on the specification: the seat height range, the seat depth and width, how far the lumbar support moves and in which directions, the armrest travel, the tested weight rating and the grade of the gas cylinder. Read those and the shortlist gets short quickly.

Start from the desk rather than the chair. A fixed desk is usually somewhere around 710 to 760 mm high, and most task chairs adjust across roughly 410 to 530 mm at the seat. If the desk cannot move, the chair has to put your forearms level with its surface and the seat has to leave your feet flat, which for shorter and taller people is a measurement problem rather than a comfort preference.