How to Calculate Your Sleep Needs

You have been told that you need 8 hours of sleep, right? Well, that may not be completely accurate. In fact, there's a lot more to the story. Since you are setting out to sleep better, it's a perfect time to figure out what your goal should be.

Tired woman lying on bed
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The Goal of "8 Hours"

Certainly 8 hours is often touted as the "average" amount of sleep an adult needs, but it is just that, an average. Let's expand that a little. The average healthy adult needs 6.5 to 8 hours of sleep each night. Even still, it is probably safe to think of this as a bell-shaped curve that extends to the extremes. There are some people who need 4 hours of sleep and others who need 10 hours. In fact, just as many people need more as those who get by with less than 8 hours. This amount also changes dramatically throughout the lifespan; consider each estimated sleep need by age:

How to Figure Out Your Personal Sleep Needs

These needs are likely determined, at least in part, by our genetics. Some people are short sleepers and others are long sleepers. It is the luck of the draw. And this tendency persists throughout life. How do you calculate what your personal needs may be?

It is relatively straightforward to figure out your sleep needs. With a few simple steps, you will know how much you need to be sleeping to feel rested. First, you need to have the luxury of getting enough sleep. You cannot allow work schedules, family obligations, hobbies, and pastimes, or other activities to encroach on your sleep period. This can be tough to arrange. The hope, ultimately, is that you will be able to go to bed and sleep until you naturally wake up. Initially, you will be sleeping off your sleep debt, but (in time) the length of your time spent sleeping will approach an average. This is your sleep need.

What if you fail to meet your sleep need? You will soon develop symptoms of sleep deprivation. Studies have shown that humans need 6.5 and 8 hours of sleep to avoid detrimental effects on daytime function (again, an average). Let's say that you calculate that you need 9 hours of sleep. Every night that you get 7 hours of sleep, you will be sleep deprived by 2 hours. It is easy to understand how important it is to determine your own need. The cumulative effect of chronic sleep deprivation may have dramatic consequences, and could even cause your death.

So once you have determined your individual sleep need, you will have established a clear goal in your efforts to sleep better. Now that you know how much you should be sleeping, your efforts can turn to improving the quality of the sleep that you get.

1 Source
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  1. Burgard SA, Ailshire JA. Gender and time for sleep among U.S. adultsAm Sociol Rev. 2013;78(1):51–69. doi:10.1177/0003122412472048

By Brandon Peters, MD
Brandon Peters, MD, is a board-certified neurologist and sleep medicine specialist.