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🌙 Wake Up Refreshed · Science-Based · Free

Sleep Calculator

Find the best time to wake up or go to sleep based on natural 90-minute sleep cycles. Wake up feeling refreshed — not groggy.

I need to wake up at:
I plan to go to sleep at:

😴 What Happens During a Sleep Cycle

Each 90-minute sleep cycle has 4 stages. Waking during Stage 3 (deep sleep) causes grogginess. Waking after a complete cycle means you are in light sleep — and feel refreshed.

Stage 1
~5–10 min Light
Stage 2
~20 min Core
Stage 3
~20–40 min Deep 😴
REM
~10–20 min Dreams

👥 Recommended Sleep by Age (WHO / NSF)

Newborns (0–3 mo)
14–17 hrs
per day
Infants (4–11 mo)
12–15 hrs
per day
Toddlers (1–2 yr)
11–14 hrs
per day
Children (3–5 yr)
10–13 hrs
per day
Children (6–12 yr)
9–12 hrs
per day
Teenagers (13–18)
8–10 hrs
per day
Adults (18–64)
7–9 hrs
per night
Older Adults (65+)
7–8 hrs
per night

❓ Frequently Asked Questions

About This Sleep Calculator

This free sleep calculator helps you find the ideal bedtime or wake time based on natural 90-minute sleep cycles. The science behind it is simple — each sleep cycle lasts approximately 90 minutes, and waking up at the end of a complete cycle (during light sleep) means you feel alert and refreshed.

The calculator adds 14 minutes of average sleep onset time so your results are accurate from the moment you close your eyes. Based on sleep science research from the National Sleep Foundation.