About SleepCalc
Science-based sleep tools, freely available to everyone.
Our mission is simple: help you wake up feeling refreshed by understanding and optimizing your sleep cycles.
Why We Built This
Everyone has experienced that groggy, disoriented feeling of waking up at the wrong time β even after a full night in bed. The problem isn't always how long you sleep, but when you wake up within your sleep cycle.
Sleep science has known for decades that humans sleep in roughly 90-minute cycles, cycling through light sleep, deep sleep, and REM. Waking up mid-cycle β especially during deep sleep β causes "sleep inertia," that foggy-headed feeling that can last for hours.
We built SleepCalc to make this science accessible. No sign-ups, no apps to download, no paywalls β just a simple, accurate calculator that tells you the optimal time to fall asleep or set your alarm.
Our Approach
Science-Based
Our calculations are based on peer-reviewed sleep research and guidelines from the National Sleep Foundation and the American Academy of Sleep Medicine.
Privacy First
All calculations happen in your browser. Your sleep data never leaves your device. No accounts, no tracking.
Free Forever
Our calculator is and will always be free. We sustain the site through advertising and affiliate partnerships.
How We Operate
SleepCalc is currently a self-funded, ad-free tool. We built it because we believe simple, science-based sleep tools should be freely available.
- If we introduce display advertising in the future (such as Google AdSense), we will update this page and our Privacy Policy before doing so. Any ads would be non-intrusive and clearly distinguished from our content.: If we introduce display advertising in the future (such as Google AdSense), we will update this page and our Privacy Policy before doing so. Any ads would be non-intrusive and clearly distinguished from our content.
- If we introduce affiliate links in the future, we will clearly mark them and update our Affiliate Disclosure page. You will always know when a link may earn us a commission.
References & Further Reading
- National Sleep Foundation β How Much Sleep Do You Really Need?
- American Academy of Sleep Medicine β Clinical Practice Guidelines
- Walker, M. (2017) β Why We Sleep: Unlocking the Power of Sleep and Dreams
- CDC β Sleep and Sleep Disorders
- NIH National Center for Complementary and Integrative Health β Sleep Disorders
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SleepCalc is an educational tool, not a medical device. We are not doctors, and this website does not provide medical advice. If you have chronic insomnia, suspected sleep apnea, or any persistent sleep disorder, please consult a qualified healthcare professional.