How wide does the rangehood need to be? This depends firstly on the width of the cooktop and secondly on the size of your kitchen. It is important for the rangehood to be slightly wider than the cooktop below it. Only then can you be certain of capturing all the rising steam and vapours and benefit fully from the rangehood's effectiveness. If there is not enough space for this, then the rangehood should be at least as wide as the cooktop. Non-standard widths of up to 240 cm are possible for many models.