HO scale
In Europe, HO scale is defined in the "" (NEM) standard "NEM 010" published by MOROP as exactly 1:87. In North America, the National Model Railroad Association (NMRA) standard "S-1.2 General Standard Scales" defines HO scale as representing 1 real foot (304.8 mm) – a ratio of , usually rounded to 1:87.1. The precise definition of HO scale varies slightly by country and manufacturer.