MyWebUtils: Free Online Dev Tools

What is a Sleep Cycle?

Your sleep isn't a single, monolithic block of time. Instead, you cycle through different stages of sleep, from light to deep and back again. One full cycle typically lasts about 90 minutes. Waking up in the middle of a deep sleep cycle is what causes that groggy, tired feeling, even if you've been in bed for a long time.

The key to waking up refreshed is to wake up at the end of a sleep cycle, when your brain is in its lightest stage of sleep.

How This Calculator Helps You Wake Up Better

This tool works backward from your desired wake-up time or forward from when you go to bed to suggest optimal times based on these natural 90-minute cycles.

• Find Your Bedtime: Tell the calculator when you need to wake up, and it will give you several ideal times to go to sleep.
• Find Your Wake-Up Time: If you're about to go to sleep, the "Sleeping Now" mode will tell you the best times to set your alarm to wake up refreshed.
• Accounts for Reality: The calculations include a 15-minute buffer, since most people don't fall asleep the instant their head hits the pillow.

Why It Recommends 7.5 or 9 Hours

Most adults need between 7 and 9 hours of sleep per night for optimal health, mood, and cognitive function. Our calculator highlights the suggestions for 5 or 6 full sleep cycles (which corresponds to 7.5 or 9 hours of sleep) as the "recommended" times to aim for.