About the Sleep Calculator
Plan your sleep around natural 90-minute cycles. Enter when you need to wake up to get the best bedtimes, or when you're going to bed to get the best wake-up times.
Key features
- Best bedtimes for a wake-up time
- Best wake-up times for a bedtime
- "Going to bed now" button
- 90-minute sleep cycles
- Adjustable time to fall asleep
- 12- or 24-hour clock
When should I go to sleep?
If you need to wake at 7:00 and it takes you about 15 minutes to fall asleep, the best bedtimes are:
| Bedtime | Cycles | Sleep |
|---|---|---|
| 9:45 PM | 6 | 9 hours |
| 11:15 PM | 5 | 7.5 hours |
| 12:45 AM | 4 | 6 hours |
The stages of a sleep cycle
| Stage | What happens |
|---|---|
| Light sleep (N1, N2) | Body relaxes, heart rate slows |
| Deep sleep (N3) | Physical recovery; hardest to wake from |
| REM sleep | Dreaming, memory and learning |
Early cycles have more deep sleep; later cycles have more REM.
Tips for better sleep
- Keep a regular schedule, even at weekends.
- Get daylight in the morning and dim lights in the evening.
- Avoid caffeine for 6–8 hours before bed.
- Keep your bedroom cool, dark and quiet.
Related calculators
Heart rate zone calculator, BMR calculator, and world clock.
How to use the Sleep Calculator
- Enter your numbers in the fields above. Units and options can be changed at any time.
- The result updates instantly as you type; there's no calculate button to press.
- Check the breakdown under the main result for the details behind the number.
- Adjust the inputs to compare scenarios, for example a different rate or term.