Sleep Calculator — Find Best Bedtime & Wake Up Time
Calculate the best time to wake up or go to sleep based on 90-minute sleep cycles. Waking at the end of a cycle means you feel refreshed — not groggy. Free sleep cycle calculator.
Last updated: June 2026
We'll show the best times to fall asleep tonight.
We'll show the best times to wake up.
Recommended times
Each suggestion is a complete 90-minute cycle, plus ~14 minutes to fall asleep. The 5–6 cycle options (7.5–9 hours) suit most adults.
Medical Disclaimer: Not medical advice. This tool is for general educational purposes only — consult a doctor for persistent sleep problems or a suspected sleep disorder.
Why 90-minute cycles?
- • Each sleep cycle lasts about 90 minutes.
- • Waking in the middle of a cycle leaves you groggy.
- • Waking at the end of a cycle feels refreshed.
- • Most adults need 5–6 cycles a night.
- • It takes about 14 minutes on average to fall asleep.
Recommended sleep by age
| Newborn (0–3 months) | 14–17 hours |
| Infant (4–11 months) | 12–15 hours |
| Toddler (1–2 years) | 11–14 hours |
| Preschool (3–5 years) | 10–13 hours |
| School age (6–13 years) | 9–11 hours |
| Teen (14–17 years) | 8–10 hours |
| Adult (18–64 years) | 7–9 hours |
| Senior (65+ years) | 7–8 hours |
Source: National Sleep Foundation guidelines.
Wake up refreshed, not groggy
Have you ever slept for eight hours and still woken up exhausted, or grabbed a short nap and felt surprisingly sharp? The difference often comes down to sleep cycles. Your body moves through repeating cycles of light sleep, deep sleep and REM sleep, each lasting roughly 90 minutes. Waking up in the deepest part of a cycle is what causes that heavy, foggy feeling known as sleep inertia, while waking at the natural end of a cycle leaves you feeling alert.
This sleep calculator works in two directions. Enter the time you need to wake up and it counts complete 90-minute cycles backwards to suggest the best times to fall asleep tonight. Or enter the time you plan to go to bed and it counts forwards to show the best times to set your alarm. Either way it adds about 14 minutes — the average time it takes a healthy adult to drift off — so the suggested times reflect when you'll actually be asleep, not just lying in bed.
The "if I sleep right now" button is handy for late nights: tap it and the calculator uses the current time to show your best wake-up options based on how many full cycles you can still fit in. The 5- and 6-cycle options (7.5 and 9 hours of sleep) are highlighted because they match the 7–9 hours most adults need, but the right amount is personal — use the result that leaves you feeling genuinely rested.
Good sleep is one of the highest-impact things you can do for your health, mood and focus, but a calculator is only a guide. Cycles vary from person to person and night to night, and consistent sleep and wake times, a dark cool room, and less screen time before bed all matter more than hitting an exact minute. Everything here runs privately in your browser, and if you regularly struggle with sleep, talk to a healthcare professional.
How it works
Three quick steps — no account, nothing uploaded to a server.
Pick a mode
Choose whether you know your wake-up time or your bedtime.
Enter the time
Type the time, or tap 'sleep right now' for instant options.
Pick a cycle
Choose a highlighted 5–6 cycle option to wake up refreshed.
General health information related to this tool is available from the US CDC sleep and health resources. Last checked July 2026.
FAQ
Frequently asked questions
How does the sleep calculator work?
Sleep happens in roughly 90-minute cycles. Waking up in the middle of a cycle leaves you groggy, while waking at the end of one feels refreshing. This calculator counts complete 90-minute cycles backwards from your wake-up time (to suggest bedtimes) or forwards from your bedtime (to suggest wake times), and adds an average 14 minutes to fall asleep so the timings are realistic.
How many hours of sleep do I actually need?
Most adults aged 18–64 need 7–9 hours per night, which is about 5 to 6 complete sleep cycles. Teenagers need 8–10 hours and older adults 7–8 hours. The calculator highlights the 5–6 cycle options (7.5–9 hours) because they suit most adults, but pick the option that leaves you feeling rested.
Why 90 minutes per cycle?
A full sleep cycle moves through light sleep, deep sleep and REM sleep, and on average that takes about 90 minutes. Aligning your wake-up time with the end of a cycle — rather than the middle of deep sleep — is what helps you wake feeling alert instead of groggy. Individual cycles vary between roughly 80 and 100 minutes, so treat the times as a helpful guide.
What is the 14-minute fall-asleep buffer?
Research suggests the average healthy adult takes around 10–20 minutes to drift off after getting into bed (this is called sleep latency). The calculator uses 14 minutes so the suggested bedtimes account for the time it takes you to actually fall asleep, not just when you lie down.
Is this medical advice?
No. This tool is for general educational purposes only and is not medical advice. If you regularly struggle to fall asleep, wake unrefreshed, snore heavily or feel sleepy during the day, speak to a doctor — these can be signs of a sleep disorder that a calculator can't address.
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