Sleep Cycle Calculator
Sleep happens in roughly 90-minute cycles. Pick whether you're planning a wake time or a bedtime to find times that align with a full cycle.
| Age group | Recommended sleep |
|---|---|
| Newborn (0–3 months) | 14–17 hours |
| Infant (4–11 months) | 12–16 hours |
| Toddler (1–2 years) | 11–14 hours |
| Preschool (3–5 years) | 10–13 hours |
| School age (6–12 years) | 9–12 hours |
| Teen (13–18 years) | 8–10 hours |
| Adult (18–64 years) | 7–9 hours |
| Older adult (65+ years) | 7–8 hours |
FAQ
Why 90-minute cycles?
Sleep moves through repeating cycles of roughly 90 minutes each, moving through light sleep, deep sleep, and REM sleep. Waking up at the end of a cycle, rather than in the middle of deep sleep, generally feels less groggy.
How many cycles should I aim for?
Most adults benefit from 5-6 full cycles per night, which works out to roughly 7.5-9 hours of sleep. This calculator shows options across that range so you can pick what fits your schedule.
Does this account for falling asleep time?
Yes — the calculator adds roughly 15 minutes to account for the average time it takes to actually fall asleep after getting into bed, so the suggested times are more realistic.
Is 90 minutes exact for everyone?
No — actual cycle length varies somewhat by individual, typically between 80-120 minutes. This calculator uses the commonly cited 90-minute average as a useful general guide, not an exact personal measurement.
How much sleep does my child need by age?
Recommended totals fall as kids get older: toddlers (1–2 years) need about 11–14 hours, preschoolers (3–5 years) about 10–13 hours, and school-age kids (6–12 years) about 9–12 hours. See the age chart above for the full range from newborn to adult.
What's the ideal nap length?
A short nap of 20–30 minutes avoids deep sleep, so you wake up more alert. A longer nap of about 90 minutes completes a full sleep cycle and can also leave you feeling refreshed — it's the 30–80 minute range in between that tends to cause grogginess, since you wake mid-cycle.
Is it bad to nap during the day?
Not generally — a well-timed nap (early-to-mid afternoon, kept short or a full 90-minute cycle) can boost alertness without affecting nighttime sleep for most people. Napping too late in the day or for too long can make it harder to fall asleep at your usual bedtime.
About this tool
This calculator works backward or forward from a target wake-up or bedtime, showing options that align with full 90-minute sleep cycles. Waking at the end of a cycle rather than mid-cycle can help you feel less groggy. This is a general guide, not medical advice.