The number of hours you sleep every night is critical for your health & mental well being.
Try to ask yourself how much sleep do I need? Or how much sleep do kids need? There is no such formula for who fits for all. It depends on your age – how old you are, how active you are in your daily life, your lifestyle and lots of other things.
Basically, If you are younger most probably need more sleep. Vice versa if you are older, you need less. You can see the chart here.