Find your optimal bedtime or wake-up time based on 90-minute sleep cycles. Wake up feeling refreshed by aligning with your natural sleep rhythm.
TooliFyra's Sleep Calculator Online Free is a science-based tool that helps you optimize your sleep schedule using the 90-minute sleep cycle formula. Waking up at the end of a cycle (rather than in the middle) leaves you feeling more refreshed and alert.
This sleep calculator online free offers two pathways: find the best time to go to bed based on your desired wake-up time, or find the best time to wake up based on when you go to bed.
Everyone can improve sleep quality by waking up at the right point in their sleep cycle. The sleep calculator online free includes a live countdown timer and accounts for fall-asleep time — 100% client-side.
Everyday Sleep — optimize your nightly sleep schedule for better rest. Shift Workers — plan sleep around irregular work hours. Students — maximize morning alertness for exams and classes.
TooliFyra's Sleep Calculator Online Free includes a live countdown timer and fall-asleep time adjustment — completely free and private with no data sent to any server.
Sleep cycles tell you when to go to bed or wake up; your age decides how much sleep you need in total. These are the recommended daily amounts published by the US Centers for Disease Control and Prevention (CDC), including naps for young children:
| Age group | Recommended sleep per day |
|---|---|
| Newborn (0–3 months) | 14–17 hours |
| Infant (4–12 months) | 12–16 hours including naps |
| Toddler (1–2 years) | 11–14 hours including naps |
| Preschool (3–5 years) | 10–13 hours including naps |
| School age (6–12 years) | 9–12 hours |
| Teen (13–18 years) | 8–10 hours |
| Adult (18–60 years) | 7 or more hours |
| Adult (61–64 years) | 7–9 hours |
| Adult (65+ years) | 7–8 hours |
For a healthy adult, five or six full 90-minute cycles (7.5 or 9 hours) fit these ranges well. Pick the wake-up time you need, use the calculator above to find bedtimes that end on a complete cycle, and allow about 15 minutes to fall asleep. Read more in our guide: How many hours of sleep do I need by age?
This calculator gives general guidance only and is not medical advice. If you regularly feel tired despite enough sleep, talk to a doctor.
A sleep cycle lasts about 90 minutes and includes light sleep, deep sleep, and REM sleep. Completing full cycles leads to more restful sleep.
Most adults need 4-6 complete cycles (6-9 hours). 5 cycles (7.5 hours) is considered optimal for most people.
Sleep cycles vary between individuals (80-110 minutes). The 90-minute average is well-established in sleep research and works well for most people.
Yes, completely free with no usage limits. All calculations happen in your browser.
