Adults need on average 8 hours sleep per night. This can very between 7 and 9 hours.
It is a very rare gene that causes people to need 6 hours sleep per night. Sleeping less than 5 hours per night will affect your well-being.
The two key ways to help yourself to get enough sleep are to always go to bed and get up at the same time every day and also to allow yourself enough time in bed to get enough sleep.