Sleep Better
Oura Crew | Nov 7, 2017

How Much Sleep Do You Need? | Ideal Sleep Duration

Entrepreneur and researcher Dan Pardi delves deep into the need for sleep in this final instalment of his three-part series.

In the preceding articles (1 and 2) in this series, we briefly reviewed the basics of sleep and wake regulation. We also discussed how timing and intensity of light exposure can affect circadian alignment, and how intelligent light exposure practices can optimize your sleep and wake patterns.

In the final article in this series, we’ll take advantage of all of this information and figure out how you can determine how much sleep you need.

Determining Your Ideal Sleep Duration

Scientists have taken many approaches to try to answer the question, “How much sleep does one need?”

A series of early studies put subjects in a stimulation-free (meaning super boring) environment for 14 to 24 hours per day, and then monitored daily sleep quantity. Each day for the first two days, subjects slept up to 12 to 20 hours! Then, on subsequent days, daily sleep times reduced until each subject arrived at a consistent daily sleep amount. Most people settled at an average of eight hours per night, although some settled closer to nine and others closer to seven.

Scientists have taken many approaches to try to answer the question, “How much sleep does one need?”

One way to interpret these findings is to assume that subjects entered these studies with extra sleep debt that built over time, due to less-than-optimal nightly sleep prior to the study. When given way-more-than-normal time for sleep in the study, this built-up pressure caused long sleep periods in the first few days, then decreased over time to settle at a unique average for each person.

More recently, sleep researchers Siobhan Banks, David Dinges, and others have been exploring this topic further. In some of their studies, they restrict sleep time during the week to four or five hours per night, then give subjects recovery sleep for several days in a row. Recovery sleep means that the subjects were allowed to sleep as long as they were able.

What they found is quite telling. Not only does performance on mental tasks increasingly degrade each day during night after night of insufficient sleep, but when finally given a chance to sleep longer, they do – much longer, in fact. It’s common for these subjects to sleep 125% of normal when given a chance, and this goes on for about four nights after this sleep restriction.

What If I Can’t Sleep Past 7am?

If you can’t sleep past the time you usually wake up in the morning, does this mean you’re getting all the sleep you need?

Well, actually, no.

Let’s say you have a fairly strong wake rhythm that starts at 7am each day. Excellent! But, even if you haven’t worn down all your sleep pressure from the night before, you still may wake up at your usual time. You just might be sleepier than you need to be under this condition.

One way to evaluate sleep need is to look at how long you can sleep.

One way to evaluate sleep need is to look at how long you can sleep. However, given this potentiality, you might just be experiencing sub-functional mental capacity during the day. In this scenario, try an experiment. Attempt to get complete nightly sleep for three weeks in a row – plus maintaining smart light habits day by day – and then see how you feel. To start, consider how much time you typically spend in bed per night by tracking it.

One objective measurement to indirectly assess sleep quality is to evaluate reaction time during the day, which is a measure of vigilance. For the first three days of the experiment, at the same time each morning, do 20 tries of a reaction time test at Write down your average reaction time across each day, then average those 3 days into one score and file it as “baseline” in a place where you can reference it later.


Day 1: 269 milliseconds (ms)
Day 2: 303 ms
Day 3: 277 ms

Baseline Reaction Time Score (3-Day average): 283 ms

Now that you have an idea of your average time in bed each night, add 30 to 60 minutes to that  time by going to bed earlier. Try not to wake by an alarm during this experiment.

Evaluate how you feel after three weeks have passed. Also, do another three days of morning reaction time tests, and see if your scores differ from your baseline. If you do see improvements, you’ve identified that you benefit by getting more sleep than your previous “normal.”

Complete Sleep

This is a term I created to describe your ideal sleep duration. When trying to determine how much sleep you need, you also must understand that your own sleep needs can change from day to day, depending on factors like fighting an infection, exercise recovery, stress, and more.

So bear in mind that your sleep need can change night to night.

My recommendation remains the same: allow for more time in bed than sleep you need. If you need eight hours of time in bed, plan to spend 8.5 hours in bed so you can wake under your own volition and not by an alarm clock. If your body needs a bit more sleep that night, you’ll have planned for this to happen. Give your body the chance to get all the sleep that it wants to get, and you will be doing yourself a favor.

Wake up on your own volition and not by external means. It’s fine to set an alarm as a stopgap but you should aim, on average, to wake naturally.

Sleep science is complex, but sleep guidance doesn’t have to be. Good sleep is extraordinarily important for your health and daily performance. The reality of the modern world requires you to counteract its forces that impair health, and this is very true for sleep. Try the recommendations covered here, and feel free to reach out and report what you found after you’ve had the chance to let your experiment run for a few weeks.

Dan Pardi is an entrepreneur and researcher whose life’s work is centered on how to facilitate healthy behaviors in others. He does research with the Psychiatry and Behavioral Sciences Department at Stanford, as well as the Departments of Neurology and Endocrinology at Leiden University in the Netherlands. His current research looks at how sleep influences decision-making.He is also the CEO of (formerly known as Dan’s Plan), a health technology company that utilizes the Loop Model to Sustain Health Behaviors – which he developed – to help people live a healthy lifestyle in a modern world.

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