Normal sleep times range from five to ten hours sleep a night. One or two people can get by on just 5 hours and another small minority needs twice that amount. Most of us, most of the time get less sleep than we need. In research studies, volunteers allowed to sleep as long as they like consistently spend an extra hour or more asleep.
To learn more about your own sleep needs consider keeping a simple sleep diary for a week or two. Every night before going to bed jot down the time and how sleepy you feel. In the morning estimate the time you actually fell asleep, whether you awakened during the night and the time you awoke. Also make a note of how alert or sleepy you feel at different times of the day, particularly when you’re not active. By reviewing this diary you can get a sense of whether you are accumulating a sleep debt. If you have access to an iPhone consider buying the Sleep Cycle App from iTunes. This is a really useful sleep analysis tool.