Sleep Calculator — Bedtime and Wake-Up by Sleep Cycles

Free sleep cycle calculator that suggests ideal bedtimes for a chosen wake-up hour, ideal wake-up times if you fall asleep now, or the perfect nap length. It uses the 90-minute cycle model plus a fall-asleep buffer, and highlights the option that matches the recommended sleep duration for your age group (based on National Sleep Foundation guidelines).

How to use the sleep calculator

1
Pick a mode

Choose "Wake up at…", "Sleep now", or "Nap".

2
Set your age group

This tailors the recommended number of cycles to your age.

3
Enter the time

Set your alarm time for wake mode; "Sleep now" and "Nap" use the live current time.

4
Adjust fall-asleep time

The average is 15 minutes — move the slider if you usually take longer or shorter.

5
Use the highlighted option

The big card is the best choice for you; other complete-cycle options appear below.

Plan bedtime and wake-up around full 90-minute cycles, tuned to your age

Set the time you need to wake up — the calculator shows bedtimes that let you wake at the end of a complete sleep cycle, with the best option for your age highlighted.

15 min
Waking at the end of a cycle feels refreshing; waking mid-cycle usually feels groggy. How many cycles you need depends on your age — the calculator highlights the best option for the age group you choose.

The 90-minute cycle is an average for planning, not a medical measurement — real cycles vary from person to person and across the night. For ongoing sleep problems, consult a healthcare professional.

Key features

Three modes
Work back from a wake time, forward from "sleep now", or time a nap — all in one tool.
Age-based recommendation
Highlights the best cycle count for teens, adults, or older adults using NSF sleep-duration guidelines.
Nap timer
Power nap, the research-backed 26-minute NASA nap, and a full 90-minute recovery cycle.
Night visualization
A hypnogram shows how deep sleep and REM shift across the cycles of your night.
Adjustable fall-asleep buffer
A 5–30 minute slider accounts for how long you actually take to drift off.
Live clock and local time
"Sleep now" updates in real time and respects your locale 12- or 24-hour format.

Frequently asked questions

Why 90 minutes per cycle?

A typical adult sleep cycle averages about 90 minutes through light sleep, deep sleep, and REM. Real cycles range roughly 80–120 minutes and shift across the night — the first cycles are shorter with more deep sleep, later ones longer with more REM. 90 minutes is the best single average for planning, not an exact biological law.

How many cycles should I aim for?

It depends on age. The National Sleep Foundation recommends 8–10 hours for teenagers, 7–9 hours for adults, and 7–8 hours for older adults — roughly 5–6 complete cycles for most people. Pick your age group and the calculator highlights the matching option instead of a one-size-fits-all number.

Why do I sometimes feel worse after more sleep?

You were likely pulled out mid-cycle, usually from deep sleep. Waking at the end of a cycle — even with slightly less total time — feels lighter than waking from deep sleep with more total time.

What is the best nap length?

For a quick boost without grogginess, keep naps to 10–20 minutes (light sleep only). The roughly 26-minute "NASA nap" is a well-known sweet spot for alertness. If you want a full 90-minute cycle, that allows deeper recovery — anything in between risks waking mid-deep-sleep and feeling worse.

How accurate is the 15-minute fall-asleep default?

15 minutes is the clinical average for healthy sleepers. Drifting off in under 5 minutes can signal sleep deprivation; regularly taking over 30 minutes can indicate stress or insomnia. Adjust the slider to your own pattern.

Does this work for shift workers?

Yes — the math is identical. Just enter your non-standard wake or sleep time and the cycle planning works the same way.

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Who is this tool for?
🎓 Students 🏥 Healthcare Professionals 👨‍👩‍👧 Parents & Families 🧘 Wellness & Meditation
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