A: It depends. Assuming that you don’t have any sleep-breathing problems and no other medical issues exist, the general range is about 5-8 hours. Everyone is different, with various sleep requirements. If you do have a sleep-breathing problem, then since your sleep quality is not as good, you’ll need more.
It’s been shown that the bare minimum "core" sleep that one needs is about 5 hours. By 5 hours, you’ll have gotten most of your non-REM deep sleep. Studies have shown that people who sleep less than 5 hours or more than 9 hours have higher rates of depression and heart disease. In short sleepers, this makes sense. But why is sleeping extra long a problem? Sleeping longer than 9 hours means that you’re not sleeping efficiently, for whatever reason. The most common problem will be a sleep-breathing problem, such as obstructive sleep apnea or upper airway resistance syndrome. If you can’t sleep on your back, or feel tired no matter how long you sleep, get evaluated by a sleep specialist.