Sleep Calculator
Find your ideal bedtime using 90-minute sleep cycles. Track sleep debt and plan the perfect nap — all based on sleep science.
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15 min
Recommended: 7h – 9h
Quality Sleep Powers Vivid Dreams
Getting the right amount of sleep — especially completing full 90-minute cycles — increases your chances of entering REM sleep, the stage where most dreaming occurs. Better sleep means better dream recall and more meaningful dream experiences.
Frequently Asked Questions
How many hours of sleep do I need?
Most adults need 7 to 9 hours of sleep per night, according to the National Sleep Foundation. Teenagers need 8 to 10 hours, and school-age children need 9 to 11 hours. The ideal amount varies by individual — factors like activity level, health, and genetics all play a role.
What is a sleep cycle and why does it matter?
A sleep cycle lasts about 90 minutes and includes light sleep, deep sleep, and REM (dreaming) stages. Most people go through 4 to 6 cycles per night. Waking up at the end of a cycle — rather than in the middle — helps you feel more refreshed and alert. This calculator times your bedtime and wake time to align with complete cycles.
How long does it take to fall asleep?
The average person takes about 10 to 20 minutes to fall asleep, known as sleep latency. This calculator defaults to 15 minutes but lets you adjust it. If you consistently fall asleep in under 5 minutes, it may be a sign of sleep deprivation.
What is sleep debt and can I recover from it?
Sleep debt is the cumulative effect of not getting enough sleep over time. For example, sleeping 6 hours instead of 8 for a week creates 14 hours of sleep debt. You can recover by adding 30 to 60 extra minutes of sleep per night over several days. However, chronic sleep debt (weeks or months) takes longer to repay and can affect health, memory, and mood.
When is the best time to take a nap?
The ideal nap window is 7 to 8 hours after waking, which typically falls between 1:00 PM and 3:00 PM for most people. This coincides with a natural dip in alertness. Keep naps under 30 minutes (power nap) to avoid grogginess, or commit to a full 90-minute cycle. Avoid napping within 8 hours of your bedtime.
How does this sleep calculator work?
This calculator uses 90-minute sleep cycle science to find optimal bedtimes and wake times. Enter when you need to wake up, and it counts backward in 90-minute intervals (plus time to fall asleep) to suggest the best times to go to bed. It also calculates sleep debt and optimal nap timing based on your schedule.