For teenagers to have good health and to function properly throughout the day teenagers need between 9 and 9 ½ hours of sleep per night.
However most teenagers today get an average of only 7 and 7 ¼ hours of sleep per night and do fine but the more sleep the better.
If you're a teenager you should aim for at least 9 hours of sleep if possible but getting 7 hours of sleep can get you by in the day.
However you'll feel much better when you're more fully rested.
Adults need around 8 to 9 hours of sleep to function properly however most adults get only 6 to 7 hours of sleep including myself.
Although sometimes I do try to catch up on sleep when I'm feeling more tired.