The wheels are the same size as ho scale. however, ho scale wheels are on axels, so that the wheel on each side of the train turn together. ( fixed to the axel) these wheels are on axels that are not fixed,. so there is a slight bit of play in them. if you place them on a ho scale flex track (for example) they are lose and slip of the track onto the rails. you need thomas track for these type trains. but as for as size goes, ho would be correct.