Choose your mode, enter a time, and press Calculate to find optimal sleep times.
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Sleep calculators by what you need
Recommended sleep by age
| Age group | Sleep per day |
|---|---|
| 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 |
| Teenager (14–17 years) | 8–10 hours |
| Adult (18–64 years) | 7–9 hours |
| Older adult (65+) | 7–8 hours |
Ranges based on widely used sleep-foundation guidance. Individual needs vary.
Sleep calculator — frequently asked
How does the sleep calculator work?+
Sleep happens in roughly 90-minute cycles. Waking at the end of a cycle feels easier than being pulled out of one mid-way. The calculator takes your wake-up time (or bedtime), adds the ~15 minutes most people take to fall asleep, and counts whole 90-minute cycles to suggest the best times to sleep or wake.
How many hours of sleep do I need?+
Most adults need 7–9 hours — about 5 to 6 complete sleep cycles per night. Teenagers need 8–10 hours, school-age children 9–11, and younger children and babies more. Older adults often need slightly less, around 7–8 hours.
Why do I wake up tired even after 8 hours?+
Waking in the middle of a deep-sleep stage leaves you groggy (sleep inertia) even after a full night. Aligning your alarm to the end of a 90-minute cycle — what this calculator does — helps you wake more refreshed. Consistent sleep and wake times matter just as much.
Is the sleep calculator a medical tool?+
No — it's a general planning guide based on average 90-minute cycles, and individual cycles vary. If you have ongoing insomnia, loud snoring, daytime sleepiness, or chronic fatigue, speak to a doctor, as these can signal a treatable sleep disorder.