The duvet must be at least 20-30 cm longer than your height, as an example, if you’re shorter than 170 cm tall, then a 200 cm duvet is appropriate for you. If your duvet is too short, you will most likely freeze your feet or your upper body, depending on where the duvet covers you. In the end, a wrong choice may result in a bad quality of sleep and you will wake up tired and with no energy.