Hello ~ glad to answer your question. Choosing the weight of dumbbells mainly depends on your own strength and quality. I am 20 years old, too. The dumbbells I am using now are a pair of 25kg, which are detachable. Dumbbell pieces are all combined with the heaviest pair of 40kg. With the deepening of exercise, strength will increase, so if you buy dumbbells with a fixed weight, buy them between 20 kg and 30 kg. Exercise is more effective and suitable for us. But I think you'd better buy a detachable dumbbell, which can be used all the time, and you can increase your weight at any time with the deepening of exercise and the increase of strength, so that the exercise effect is more obvious ~ I bought a 40kg electroplated dumbbell from Taobao, 280 yuan, from 20 yuan to Zhou Hao.