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Sleep Calculator
Work out the best time to go to bed or wake up using 90-minute sleep cycles, all computed in your browser.
HOW TO USE
- 1Choose whether to plan by desired wake time or bedtime.
- 2Pick the time and how many sleep cycles you want (4 to 6).
- 3Read the recommended time and the full cycle list in the results.
EXAMPLE
INPUT
Wake time: 7:00 AM · Cycles: 5
OUTPUT
Bedtime: 11:15 PM (previous day) · Bedtimes for 1 to 5 cycles: 5:30 AM, 4:00 AM, 2:30 AM, 1:00 AM, 11:30 PM (previous day)
FAQ
Why 90 minutes per cycle?
A sleep cycle, light, deep and REM sleep, averages about 90 minutes. Waking during deep sleep leaves you groggy; waking at the end of a cycle leaves you more rested.
How many sleep cycles should I get?
Most adults need 4 to 6 cycles (6 to 9 hours). 5 cycles is a common target. Children and teens typically need more sleep than adults.
Why is there a 15-minute buffer?
Most people take about 10 to 20 minutes to fall asleep after getting into bed. The calculator adds 15 minutes so your cycles complete by your target time.
Is this medically accurate?
Sleep cycles vary in length from person to person and night to night. This is a general planning guideline, not a medical prescription. For chronic sleep problems, consult a healthcare provider.