Around four to six hours, always trying to get to bed early though. For me it mainly depends on the existing workload and the allotted deadlines of the projects.
I sleep for 6-7 hrs a day if I am physically fit. When I am unfit it increases When exam arrives it decreases and I lose weight also..
I don't sleep much at all, but it's not for a lack of trying. I average about 3-4 hours a night, total, not in a row. I typically wake up about every 30-45 minutes. If I'm actually working on code, or designing graphics, I may go 40 hours w/o sleep. Although, I do sleep very well after that amount of time being awake.