A free sleep calculator that finds bedtimes and wake times at the end of a full sleep cycle, drawn on a 24-hour clock.
Find the bedtime or wake time that ends a full sleep cycle, so you wake up less groggy.
Your night
Your result
To wake at 7.00, go to bed at 23.15 for five full cycles, or 21.45 for six.
Bedtimes that end a cycle
| Bedtime | Cycles | Sleep | For adults |
|---|---|---|---|
| 21.45 | 6 cycles | 9 h | 7 to 9 hours |
| 23.15 | 5 cycles | 7.5 h | 7 to 9 hours |
| 0.45 | 4 cycles | 6 h | Short |
| 2.15 | 3 cycles | 4.5 h | Short |
A cycle is about 90 minutes, and it takes about 15 to fall asleep. The National Sleep Foundation recommends 7 to 9 hours a night for adults under 65, and 7 to 8 after.
How it's worked out
7.00 − 450 minutes (5 cycles of 90) − 15 minutes to fall asleep = 23.15.
Source: National Sleep Foundation
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These calculators give general estimates for healthy adults, not medical advice. Talk to your doctor before you change how you eat or train, especially if you're pregnant, take medication or have a health condition.
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Paste the code into any page: WordPress, Webflow, Squarespace, Ghost or plain HTML. It's free with the credit under it, which links back to navid.me.
This free sleep calculator finds the bedtime or wake time that ends a full sleep cycle, so your alarm goes off between cycles instead of in deep sleep.
Pick when you need to wake up, or when you're going to bed, and it shows every time that fits on a 24-hour clock.
I built it because waking in the middle of a cycle is a big part of why some mornings feel heavy. Counting cycles back from your alarm is a simple fix, and the clock makes it easy to see.
Here's how sleep cycles work, how much sleep you need, and how to make the times stick.
TL;DRKey takeaways
What is a sleep calculator?
A sleep calculator counts sleep cycles back from your wake time, or forward from your bedtime. Each cycle runs through light sleep, deep sleep and REM, and lasts about 90 minutes.
Waking at the end of a cycle, in light sleep, tends to feel easier than waking from deep sleep in the middle of one.
How to use the sleep calculator
It takes one choice and one time.
Your choice stays in this browser.
A worked example
Here's the example the calculator loads when you press Try an example.
You need to wake at 6:30 am. Counting back five cycles of 90 minutes, plus 15 minutes to fall asleep, gives a bedtime of 10:45 pm.
- Cycles
- 6
- Sleep
- 9 h
- Cycles
- 5
- Sleep
- 7.5 h
- Cycles
- 4
- Sleep
- 6 h
- Cycles
- 3
- Sleep
- 4.5 h
Five or six cycles fit the 7 to 9 hours adults need. Four cycles is short, so save it for nights you can't avoid.
How much sleep you need
The National Sleep Foundation recommends 7 to 9 hours a night for adults aged 26 to 64, and 7 to 8 for those 65 and older.
Cycles aren't exactly 90 minutes for everyone, and they change through the night. Use the times as a guide, and adjust by 15 minutes if you still wake groggy.
How to make it stick
Good times only help if your nights follow them.
Keep the same wake time
Waking at the same time every day, weekends too, sets your body clock better than anything else.
Cut the light at night
Dim the lights and screens in the last hour before bed.
Light is the enemy of sleep, full stop.
Build a wind-down
The daily schedule maker puts a wind-down into your evening, and the morning routine generator plans the other end.
Mistakes to avoid
These are the common ways a sleep plan falls apart.
- Sleeping in on weekends and shifting your clock
- Counting time in bed as sleep
- Screens in bed right up to the minute you sleep
- Caffeine late in the day
Fix your wake time first, and the bedtime follows.
Sleep is the base
Sleep shapes your energy, focus and mood the next day.
Sleep is the single most effective thing we can do to reset our brain and body health each day.
Why We Sleep by Matthew Walker explains what happens in each stage of the night.
Why We Sleep
Why We Sleep by Matthew Walker reveals how sleep affects every aspect of our health and success.
I may earn a commission if you make a purchase, at no additional cost to you.
Who is the sleep calculator for?
It's for anyone who wakes up groggy or wants a steadier night, and these tools help with the rest of the day.
- Morning routine generator – for a calm start after you wake
- Daily schedule maker – for fitting sleep into the rest of your day
- Longevity routine – for sleep, food and training together
- Water intake calculator – for the other daily basic
- Time zone converter – for planning sleep across time zones
Pick your wake time here, then keep it every day for two weeks.
More health calculators
Every health calculator shares the same scene and music, so the page feels the same wherever you go.
| Calculator | What it answers |
|---|---|
| Water intake calculator | How much should I drink? |
| TDEE calculator | What do I burn in a day? |
| Running pace calculator | What's my pace? |
| BMI calculator | Is my weight healthy for my height? |
Good sleep makes every other number on this list easier to move.
Plan your health with your AI
Take your numbers further in
Sleep Calculator FAQs
Questions about the sleep calculator? Here's what to know.
A sleep calculator finds bedtimes or wake times that end a full sleep cycle.
This free one counts 90-minute cycles and shows your night on a 24-hour clock.
About 90 minutes, though it varies between people and through the night.
Go to bed at 10:45 pm for five cycles, or 9:15 pm for six.
That counts 15 minutes to fall asleep.
The National Sleep Foundation recommends 7 to 9 hours for adults aged 26 to 64, and 7 to 8 for those 65 and older.
Waking from deep sleep in the middle of a cycle can feel heavy.
Short sleep and a moving wake time make it worse.
7.5 hours, or five cycles, fits the recommended range.
Six hours is short for most adults.
It usually takes about 15 minutes, which the calculator adds.
Yes, a steady wake time does more for your body clock than anything else.
No, it's a general estimate for healthy adults.
Talk to your doctor before you change how you eat or train, especially if you're pregnant, take medication or have a health condition.
Yes, it's free with no login.
I did.
I'm Navid Moazzez, and I made the sleep calculator as one of my free tools on navid.me.
More about me.
Navid Moazzez
AI business strategist & AI OS builder
Navid Moazzez helps creators and founders master AI and build their own AI Operating System (AI OS) to automate their business and life.
Navid.me is reader-supported. When you buy through links on this site, I may earn an affiliate commission. Learn more.
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