Sleep Smarter. Wake Up Refreshed.
Science-based sleep calculators built on 90-minute sleep cycle research. Find your perfect bedtime, track your sleep debt, and optimise your rest — free, instant, no login required.
Six Free Sleep Calculators
Choose the tool that matches what you need tonight
Sleep Calculator
Enter your wake-up time and get the perfect bedtime based on 90-minute sleep cycles.
Use Calculator →Bedtime Calculator
Find the ideal time to go to bed tonight based on when you need to wake up.
Use Calculator →Sleep Cycle Calculator
See how many complete sleep cycles you get each night with a visual stage breakdown.
Use Calculator →REM Sleep Estimator
Find out how much REM dream sleep you are getting and whether it is enough for your age.
Use Calculator →Sleep Debt Calculator
Log 7 nights of sleep and discover exactly how much rest you owe your body.
Use Calculator →Nap Optimizer
Find the perfect nap length for your goal — energy boost, better memory, or full recovery.
Use Calculator →How It Works
🎯 Choose Your Calculator
⏰ Enter Your Times
instant results, no sign-up needed
😴 Sleep Better Tonight
Why Sleep Cycles Matter
Your body sleeps in 90-minute cycles, each containing four stages: light sleep (N1), core sleep (N2), deep restorative sleep (N3), and REM dream sleep. Waking at the end of a complete cycle — rather than in the middle of deep sleep — is the single biggest factor in whether you feel refreshed or groggy in the morning.
Most adults need 5 complete cycles (7.5 hours) per night. But it is not just about total hours — it is about timing. Our calculators help you hit cycle boundaries naturally so every morning feels like a good one.
Learn more about sleep science →