In fact, how many push-ups you can do is not a measure of how many kinds of dumbbells you can do. Can do 50-65 push-ups. If you want to get better exercise, you should do heavy push-ups, because push-ups are exercises for your back and chest. If you want to exercise your back, I can't give you an accurate answer. You should buy more dumbbells, because using dumbbells and doing push-ups have a completely different feeling on your back.

So I give you roughly divided into three categories:

If you are a beginner in the field of fitness, then I recommend you to buy a dumbbell ranging from 15 kg to 20 kg.

If you have been playing fitness for a while, then you can consider 30-50 kg.

If you are a master, then I don't need to say more, and you will know how many dumbbells you need to practice.

I hope what I wrote is more or less helpful to you (absolutely original).