Sleep Calculator
Based on 90-minute sleep cycles. Find the perfect time to wake up, go to sleep, or discover how much sleep your body actually needs.
To wake up feeling refreshed, go to sleep at one of these times:
Based on 90-minute sleep cycles + 15-minute average fall-asleep time (National Sleep Foundation).
90-Minute Cycles
Your brain cycles through light sleep, deep sleep, and REM roughly every 90 minutes. Waking at the end of a cycle means less grogginess.
15-Min Fall-Asleep Buffer
The average person takes about 15 minutes to fall asleep. This calculator accounts for that so your times are accurate.
Age-Based Recommendations
The CDC publishes sleep duration guidelines by age group. Our duration calculator uses these to flag if you're under-sleeping.
Frequently Asked Questions
What is a sleep calculator?▾
A sleep calculator helps you find the best time to wake up or go to sleep based on your body's natural 90-minute sleep cycles, so you wake up feeling refreshed instead of groggy.
How many sleep cycles do I need?▾
Most adults need 5–6 complete sleep cycles (7.5–9 hours) per night. Each cycle lasts approximately 90 minutes and includes light sleep, deep sleep, and REM sleep stages.
Why do I wake up groggy even after 8 hours?▾
Grogginess often occurs when you wake up in the middle of a deep sleep stage. This calculator times your alarm to the end of a complete cycle to minimize grogginess.
How long does it take to fall asleep?▾
The average person takes about 15 minutes to fall asleep. This calculator accounts for this buffer when calculating your ideal wake-up or bedtime.