How big should the rental advertisement on the sixth floor be printed?

Between 48 and 80. The font size of 40-80 cm can be applied to most billboards. The font size in this range allows people to see the advertising language from a long distance, but it is not too small to see clearly. Broadly speaking, advertising words refer to a kind of propaganda language that introduces goods, culture, entertainment and other services to the public through various media and posters.