I roll into bed around 10:30 or 11:00pm, to wake up at 6:30.
Assuming I sleep the whole time, that makes it look like I'd be getting about ~8 hours on average.
Factor in it takes about 20-30 minutes to fall asleep, brings it down to ~7:30 hours of sleep.
Factor in time spent tossing and turning during the night, laying in bed in that "I'm not fully awake, but I'm damn sure not asleep" mode, and that brings it down to at least ~5:00 hours of sleep, if not less. This isn't every night, but it is common.
Added to that, my s/o works odd hours, and so I get woken up at least once per night about 3 hours before 6:30 am no matter what, which means i'll spend the next 20-30 falling back asleep, if I can - some times it's a few hours of the aforementioned not sleeping / not waking phase.
On a good night, my quality sleep is probably 6 hours.
On a bad night, probably 2 to 3.