Sleep Calculator

Waking up in the middle of deep sleep can leave you feeling tired and cranky. This tool helps you plan your sleep around natural body rhythms so you wake up refreshed and full of energy every morning.

What do you want to calculate? I know when I want to wake up I know when I am going to bed

Target Time:

How It Works

Our brains do not just shut off when we sleep. Instead, they move through different sleep stages. A complete sleep cycle lasts around 90 minutes. During this time, your body goes from light sleep, down into deep sleep, and into dreaming sleep before starting over again.

If your alarm rings while you are in deep sleep, your body feels shocked. This causes morning grogginess. Waking up at the end of a 90-minute cycle feels natural and easy because your body is already in light sleep. This calculator counts in 90-minute blocks and adds 15 minutes for the average time it takes to fall asleep.

Related Tools

Looking for other helpful ways to plan your rest? Try these tools:

• sleep cycle calculator — Find out how many total rest cycles you need each night.
• wake up time calculator — Choose the best morning alarm based on when your head hits the pillow.
• bedtime calculator — Learn the exact hour to turn off your lights for a set morning schedule.

Frequently Asked Questions

How many hours of sleep do I need? Most adults need between 7 and 9 hours of rest each night. Kids and teenagers need even more, usually between 9 and 11 hours, because their bodies and brains are still growing.

Why do I feel tired after 8 hours of sleep? Getting enough hours is only half the battle. If your alarm wakes you up from deep sleep in the middle of a cycle, you can still feel sluggish.

How long does it take to fall asleep? Most healthy people take about 10 to 20 minutes to drift off. Our calculator uses a 15-minute average to give you the most accurate times.