Sleep Calculator – Find Your Best Bedtime
Calculate when to sleep or wake up based on 90-minute sleep cycles. Getting the right number of cycles helps you wake up refreshed instead of groggy.
Includes 15 min to fall asleep
09:45 PM
6 cycles (9h)
11:15 PM
5 cycles (7.5h)
12:45 AM
4 cycles (6h)
02:15 AM
3 cycles (4.5h)
How to Use
- 1
Choose 'Wake up at' or 'Sleep at' depending on your schedule
- 2
Enter your desired wake-up or bedtime
- 3
Pick a sleep time from the results — 5 or 6 cycles is recommended
Frequently Asked Questions
How long is a sleep cycle?
A typical sleep cycle lasts about 90 minutes and includes light sleep, deep sleep, and REM sleep. Most adults need 4–6 cycles per night.
Why is it better to wake up between cycles?
Waking up mid-cycle — especially during deep sleep — leaves you feeling groggy and disoriented. Waking at the end of a cycle means you surface naturally from lighter sleep.
How many hours of sleep is ideal?
Most adults need 7.5–9 hours (5–6 cycles). The exact amount varies by age and individual need, but consistently getting fewer than 6 hours is linked to health risks.
Does the 15-minute fall-asleep estimate apply to everyone?
The 15-minute offset is an average. If you fall asleep faster or slower, adjust your bedtime accordingly to hit a cycle boundary at your actual wake-up time.
Wake up at the right time
A sleep calculator suggests the best times to go to bed or wake up by working in full sleep cycles of about 90 minutes. Waking at the end of a cycle, rather than in the middle of deep sleep, helps you feel more rested.
Tell it when you need to wake, and it shows the bedtimes that line up with complete cycles.
Planning sleep around a fixed alarm
- Planning a bedtime around a fixed alarm.
- Working out when to wake from a nap.
- Building a more consistent sleep routine.
- Set the alarm with the countdown timer.
Your sleep times stay private
Times are calculated in your browser. Sleep needs vary by person — use it as a guide.