Sleep Calculator Guide
This guide explains how to use the sleep calculator, what sleep cycles mean, and how to choose a bedtime or wake-up time that feels better in real life — including sleep recommendations by age.
Table of Contents
1) How to use the sleep calculator
- Choose your age group (Preschool, School-age, Teen, Adult, or Older adult).
- Set the time you want to wake up using the hour/minute controls.
- Tap Calculate bedtime to see ideal bedtimes.
- Or tap Calculate wake-up time if you want to sleep now.
Tip: If you usually feel groggy, try a different result tomorrow (one step earlier or later). Small shifts can make a noticeable difference.
2) Sleep cycles explained (90 minutes)
Sleep is often described in cycles that repeat through the night. A commonly used estimate is ~90 minutes per cycle. Waking closer to the end of a cycle may help you feel less “hit by a truck” compared to waking mid-cycle.
This is why the calculator shows multiple options — they’re different “end-of-cycle” times.
Want a bedtime that actually feels better? See your results in the sleep calculator.
3) How to choose the best bedtime
If you can choose only one bedtime, pick a time that:
- Gives you enough total sleep for your age group
- Fits your morning schedule consistently
- Feels realistic (you’re more likely to stick to it)
Consistency matters. A slightly “imperfect” bedtime you follow daily often beats the “perfect” bedtime you follow once.
You can experiment with different schedules using the bedtime calculator to see which option helps you wake up feeling refreshed.
You can experiment with different schedules using the bedtime calculator to see which option helps you wake up feeling refreshed.
4) “If you go to bed now” — how to use it
This option is for nights when you’re about to sleep immediately. It estimates good wake-up times starting from the current moment, using: a 15-minute fall-asleep buffer plus full sleep cycles.
If you need to wake up soon, try choosing fewer cycles (shorter sleep). If you have time, pick a later option for more rest.
5) Recommended sleep by age
| Age Group | Recommended Sleep |
|---|---|
| Preschool (3–5) | 10.5–13.5 hours |
| School-age (6–12) | 9–12 hours |
| Teen (13–18) | 7.5–10.5 hours |
| Adult (19–64) | 6–9 hours |
| Older adult (65+) | 6–9 hours |
These ranges are general guidance. Individual needs can vary based on activity, stress, health, and sleep quality.
6) Using the calculator for naps
For a nap, many people prefer:
- ~90 minutes (one full cycle)
- ~180 minutes (two full cycles)
If short naps make you feel worse, try a full-cycle nap instead of a random length.
7) Sleep calculator FAQs
How does the sleep calculator work?
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How does the sleep calculator work?
▼It estimates ideal bedtimes and wake-up times by aligning with approximate 90-minute sleep cycles and adding a typical 15-minute fall-asleep buffer.
Why does the calculator use 90-minute sleep cycles?
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Why does the calculator use 90-minute sleep cycles?
▼A full sleep cycle is often approximated at about 90 minutes. Waking near the end of a cycle may reduce grogginess compared to waking in the middle of a cycle.
What does the 15-minute fall-asleep buffer mean?
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What does the 15-minute fall-asleep buffer mean?
▼Many people take roughly 10–20 minutes to fall asleep. The calculator uses 15 minutes as a simple average so results are more realistic than starting cycles immediately.
Which result should I choose: the earliest or the recommended one?
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Which result should I choose: the earliest or the recommended one?
▼If you can, choose a time that gives you more total sleep and still fits your schedule. If you feel groggy often, try a different option the next day (earlier or later) and see how you feel.
Can I use this sleep calculator for naps?
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Can I use this sleep calculator for naps?
▼Yes. Many people find 1 cycle (~90 minutes) or 2 cycles (~180 minutes) helpful depending on how tired they are and how much time they have.