This study investigated the impact of booth size on productivity during brief web conferences in private work booths. The booths, constructed from rigid cardboard, were tested in four conditions. Objective assessments included heart rate, cerebral blood flow, and speech duration measurements, while subjective assessments involved booth impression, conference evaluation, and concentration ability questionnaires. Objective measures suggested the minimal influence of booth size on physiological responses, indicating similar conference performance across conditions. However, subjective evaluations indicated decreased comfort and perceived conference quality with smaller booth sizes. The threshold for reduced comfort and quality was identified between booth widths of 800 mm and 700 mm. Some found a moderate enclosure of 800 mm most conducive to concentration, while others preferred a wider space of 1200 mm, indicating individual preferences for booth size. The study suggested that while objective measures suggest minimal influence, subjective evaluations indicate the need for a certain size to ensure comfort and a “just right” size for stimulation.