9-inch folding fan 29.97 cm. The total length of folding fan is generally defined by the old unit "inch". Generally speaking, the most conventional folding fan size is 90/20, that is, the overall length of the folding fan is 9 inches, and the width of the air outlet is 2 cm. According to the length unit, one inch is 3.33 cm and nine inches is 9×3.33=29.97 cm.