I think about 16 hours I remember going to bed at midnight and then waking up around 4 pm and just wondering how in the hell I actually managed to sleep that long. 

In my defense I'd been up for 2 days straight, but still.

Probably around 16 hours. My parent usually wake me up. I would sleep all day if I was allowed to.

I would say I have slept anywhere from 12-18 hours at most at once. I tend to sleep about 6.5-7 hours on weekdays and probably 10 on weekends. I think that is pretty normal in my opinion, f9r the most part I sleep for normal amounts of time but when I am really exhausted I could sleep all day long. But at most I think I have slept 14 hours, maybe 15 at once tops. No more, no less XD

The longest time I have slept at once is almost eleven hours. I slept that long because I woke up early in the morning and then I stayed up really late at night. I was tired for a little while after that!

The longest I have slept for is 11 hours, I can't remember why I could sleep so long on that night but it was one of the best nights sleep I have ever had.

I remember than I slept for 10 hours and when I woke up not knowing where I was

This is a good question! 
I used to hate sleeping when I was younger but I realized how important sleeping is. 

The longest time I've slept was a whole day! 
 

EideticMemory : I think about 12 hours once when i was in egypt visiting family. I was dog tired after i had to be up very VERY long.

EideticMemory : 26 hours i skiped a day it was wierd i wonder why nobody woke me up

I think the longest I've slept at once is around 13-14 hours.
It's kind of odd since I don't remember doing anything tiring I was just really tired for some reason.

Not really sure, but I think that I have slept for 11 hours. I normally only sleep for 3-8 so I am not the kind of person who will sleep a whole lot at one time.

I slept for about 18 hours one day because I was grounded so I just stayed in bed all day

26 hours. I had been awake for 2 weeks straight with only 1-2 hours of sleep each day. I slept for that long straight. I don't know how.

I think it was about 17 hours. I remember playing final fantasy 13 for like 35 or so hours straight and I could barely keep my eyes open. I crashed at about 5 am and woke up at 10 pm. The worst part about it was that I woke up still feeling tired. 

I believe I slept for twenty-one hours once. I believe it was when I was in third grade. It was absolutely horrible. We went to Virginia because I have a great aunt and uncle who live there. They live on a farm in the mountains, and there is a lot of pollen. I thought it was bad here in Pennsylvania before we left, and I was proven wrong. I could barely breathe. Oh, I should probably mention that I am rather allergic to pollen. It is not all that deadly, but the symptoms can get pretty severe, and I suffer immensely. I feel like it got so bad that you could actually see the pollen in the air in some spots. Anyways, it got so bad that I was bed-ridden. I slept for twenty-one hours, and when I woke up, it got worse. I ended up getting pneumonia, and they had to take me to a doctor. Unfortunately, the nearest doctor was an hour away... so I had to suffer the entire way there and back, unable to go to sleep after my exceedingly long nap. At the time, I was unable to swallow pills, so they gave me the worst tasting medicine I have ever had in my life. I remember it being akin to sand paper and it was white. That was, coincidentally, the worst few days of my life, and my longest time of sleep fell on those days. We stayed there for about seven days. My family wanted to stay longer, but realized that they had to get me out of there before I died. I probably actually would have, now that I think about it. I was so glad to be away. It was absolutely horrible. I really hope I never have to experience anything like it again.

maybe about 10-12 hours. I don't sleep for very long at all. I usually sleep for about 7-9 hours actually.

I think the longest I've ever slept is 13 or 14 hours, which I did last week. I was outside for a few hours that day, it was warm, and I had a cold that was starting. Needless to say, I was more than ready for bed that night.

I've probably slept for around 20 hours once, can't remember why but it was probably because I was really sick and wanted to make sure my body was fully recovered before I resumed life.

The longest that I've ever slept is for about 18 hours. I was completely tired from an assignment that I've been working for the past couple of days, and when I finally got done with it, it was in the weekend, so I had I chance to rest. I slept from 9 pm, all the way to about 2 or 3 pm the next day. My family didn't bother with waking me up because they knew I was working hard the previous days. I don't get that much sleep and I don't like to do so though.