Wake up refreshed every morning. Calculate the perfect bedtime or alarm time based on 90-minute sleep cycles.
⏰ What time do you want to wake up?
:
💤I usually fall asleep in about
AD · Google AdSense
🧠 The Science of Sleep Cycles
→Each sleep cycle lasts approximately 90 minutes and includes light sleep, deep sleep, and REM sleep.
→Waking up at the end of a cycle means you wake during light sleep — feeling alert and refreshed.
→Waking up mid-cycle causes sleep inertia — that groggy, disoriented feeling that can last hours.
→Most adults need 5–6 complete cycles (7.5–9 hours) per night for optimal health.
💡 Better Sleep Tips
→Avoid screens for 30–60 minutes before bed — blue light suppresses melatonin production.
→Keep your bedroom cool (16–19°C) — your body temperature needs to drop to initiate sleep.
→Stick to a consistent sleep schedule, even on weekends — your circadian rhythm loves routine.
→Avoid caffeine after 2pm — it has a half-life of ~6 hours and stays in your system longer than you think.
About This Sleep Calculator
This sleep calculator suggests the best times to go to bed or wake up by working around 90-minute sleep cycles. Waking at the end of a cycle, rather than in the middle of deep sleep, can help you feel more refreshed.
This is general information only, not medical advice. Sleep needs vary between people. If you regularly struggle with sleep or feel tired despite enough hours, speak with your GP.
Frequently Asked Questions
How long is a sleep cycle?+
A full sleep cycle lasts roughly 90 minutes and moves through light, deep and REM sleep. Most people go through four to six cycles a night.
How much sleep do I need?+
Most adults need around 7–9 hours. Quality and consistency matter as much as the total number of hours.
Why do I feel groggy even after enough sleep?+
Waking in the middle of a deep sleep stage can leave you groggy. Aligning your wake time with the end of a cycle can help.