Sleep Calculator: How Much Sleep Do You Need?

July 1, 2021 | Casper Editorial Team
Illustration of a clock on a purple background Illustration of a clock on a purple background Illustration of a clock on a purple background

Waking up some days can feel refreshing while others feel like it’s almost impossible. Even when you get a relatively consistent amount of sleep each night, you can feel drowsy some days and alert on others. So why is this?

Sleep is more than just how much time you slept. You also have to consider your sleep cycles, which are the stages your body goes through each night as you sleep. 


To help you understand how much sleep you need, use our sleep calculator to determine what time to wake up or go to sleep, based on your sleep cycles.

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*According to National Sleep Foundation Guidelines

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What is a Sleep Cycle?

Contrary to popular belief, the amount of time you spend sleeping doesn’t guarantee a good night’s rest. Although sleep duration is important, it’s also critical to focus on your sleep cycle.

Sleep cycles are the stages your body goes through each night as you snooze. There are four total stages in a sleep cycle, each lasting a different amount of time. 

On a typical night, the average person goes through four to six sleep cycles that last around 90 minutes each. However, not all sleep cycles are the same length and vary depending on different factors such as age, sleep patterns, and personal preferences.

Wake-up Time Bedtime
7.5 Hours of Sleep
5 cycles
9 Hours of Sleep
6 cycles
5 a.m. 9:15 p.m. 7:45 p.m.
6:30 a.m 10:45 p.m. 9:15 p.m
8 a.m 12:15 a.m 10:45 p.m.
9:30 a.m. 1:45 a.m. 12:15 a.m.

It’s typical for your sleep cycles to change as you progress through a night’s worth of sleep. The first sleep cycle you go through is usually the shortest, ranging from 70 to 100 minutes. Later cycles will range from 90 to 120 minutes, but the composition of each cycle will change as the night goes on.

What Are the Stages of Sleep?

There are four total sleep stages. One for rapid eye movement (REM) and the other three that form non-REM (NREM) sleep. Each stage is determined by the brain activity while you sleep, which shows distinct patterns that identify a specific stage. 

Sleep Stage Type of Sleep Length
Stage 1 NREM 1–5 minutes
Stage 2 NREM 10–60 minutes
Stage 3 NREM 20–40 minutes
Stage 4 REM 10–60 minutes

Stage One

Stage one is often referred to as the transition stage and lasts only one to five minutes. During this time, the sleeper hasn’t fully relaxed their body, but the brain starts to slow down and lightly changes in activity associated with falling asleep. The body soon follows, with occasional movements like twitches. 

Stage Two

Once you’ve entered stage two, your muscles relax, your body temperature drops, and your breathing and heart rate slow. At the same time, your brain activity changes and eye movements stop. In this stage, it’s harder to be woken up by external stimuli and it lasts about 10–16 minutes.

Stage Three

Stage three is known as deep sleep, where the body further relaxes and restores itself to help with growth and recovery. Not only that, but this stage is critical for overall health as it can also aid the immune system and other key bodily functions. You spend an average of 20–40 minutes in this stage, but it gets shorter as the night goes on as you spend more time in REM sleep. 

Stage Four

Stage four is also known as rapid eye movement (REM) sleep. During this stage, brain activity picks up and the body experiences several changes including rapid eye movement, increased heart rate, fast breathing, and atonia. Atonia is a temporary paralysis of the muscles, with the exception of eyes and breathing muscles. This paralysis is a protective measure to ensure you don’t harm yourself by trying to act out your dreams.

How Much Sleep Do You Need?

How much sleep you need changes as you age. The older you get, the less sleep you need. For instance, infants may need up to 17 hours of sleep while adults can settle for about seven hours of sleep each night. 

According to the CDC, this is the general amount of sleep each age group needs for optimal health:

Age Hours of Sleep Needed
0–3 months 14–17 hours
4–11 months 12–16 hours
1–2 years 11–14 hours
3–5 years 10–13 hours
6–12 years  9–12 hours
13–18 years 8–10 hours
19–64 years 7–9 hours
65+ years 7–8 hours

These guidelines are great to keep in mind but don’t feel limited to them. Some people feel more rested with a few extra hours of sleep while others find that a minimum of seven hours is perfect for them. What matters are your individual sleep needs and what makes you feel the most rested. 

Sleep Calculator FAQ

A sleep calculator is a great tool to use when you’re trying to optimize your sleep and overall health. However, a sleep calculator can’t answer all of your specific questions. To help, check out a few of these commonly asked questions, so you can find the right sleep schedule for you.

Is it Better to Sleep in 90-Minute Cycles?

On average, a full sleep cycle lasts around 90 minutes, but everyone is different. Some people may last longer in a certain stage of sleep than others. Not only that but the duration of your sleep cycle changes throughout the night. What matters the most is that you achieved the right amount and quality of sleep that night.

What Is the Ideal Time to Sleep and Wake Up?

There is no specific time that is ideal to sleep and wake up. The exact time all depends on you and your lifestyle. If you have a specific time you wake up each morning, adjust your bedtime to the minimum amount of sleep time you need based on your age. However, our biological clocks work around the sun, so going to bed earlier and waking up earlier is ideal. 

Is it OK to Get 5 Hours of Sleep?

Life happens and things can’t always go our way, so getting 5 hours of sleep is okay every once in a while. However, regularly getting five hours of sleep each night is not enough, and in the long-term, it can affect the body’s ability to function properly. It is recommended that adults receive at least seven hours of sleep each night for optimal health.

Do You Get Less Deep Sleep as You Get Older?

It’s true that getting older results in getting less deep sleep at night. This is because your body produces lower levels of growth hormones, so you’ll experience a decrease in deep sleep. As this happens, your body produces less melatonin which means you’ll experience more fragmented sleep.

Getting optimal sleep isn’t as simple as snoozing for seven to eight hours each night. You have to consider multiple factors including your age, lifestyle, and sleep hygiene since sleep is unique to each individual. To help you determine how much shut-eye you need, use our sleep calculator to determine the best sleeping schedule for you.

To help enhance your sleeping experience, invest in a cozy mattress tailored to your specific needs along with a super soft sheet set to match.