How much sleep do humans really need to survive?

However long it takes before you aren't tired anymore

Sleeping cycles are thought to be multiples of 90 minutes

i.e. 1.5 hours, 3 hours... 6 hours, 7.5 hours

The 8 hour recommended sleeping time does not apply to most people specially after they reach certain younge adult ages.

I couldn't agree with you more on the idea that sleeping is a waste of time, if you asked me this question a few years ago. I would've said, "thinkg about it, at this rate, when you're 60, you'll have spent one third of your life asleep!"

The trick is however, to sleep as much as you think/feel you need to. For example, if you're falling asleep during the day when you should be awake, you might need more sleep.

On the other hand, if you're having trouble falling asleep, you might not be tired enough yet.

At the moment, I try to keep the minimum 4.5 hours of sleep and push it up to 6 hours when I feel tired or have a busy schedule the day after.

It depends on the person, but 8 hours is the optimum. There are stories of people, like Thomas Alva Edison, who only slept about one hour every night and took catnaps throughout the day. But researchers have also found that people who are forced to stay awake start having severe physical and and mental problems, including increased risk for disease and even hallucinations. Even stopping REM sleep causes hallucinations. Your body needs sleep to regenerate itself.

8 but most of the time i get by on 3 or 4 hours

I guess any amount of sleep is needed to survive. It is generally recommended to get roughly 7-8 hours of sleep every night.

8 or 9 hours

8-9 hours

There are no documented cases of a healthy human dying from total sleep deprivation (excluding accidents). In carefully monitored experiments, several normal research subjects stayed awake for 10 days. While they all experienced cognitive deficits in memory, concentration, etc, none of them experienced serious medical, neurological, physiological or psychiatric problems.

so i say stay awake as long as you want. when you can't take it anymore your body will let you know

not sure, but I once saw a documentary about people who were given 20 minutes sleep every four hours and they lasted a month before they got to the point where they could not be kept awake.

I think 5-6 hours is enough. Best wishes