By CalculatorInn Team · Updated: 2026-03-22 · Free & accurate · Instant results
Find the best bedtime or wake-up time based on sleep cycles. Waking between cycles (not during deep sleep) helps you feel more rested.
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Sleep Cycles = 90 minutes each; Fall Asleep Time ≈ 15 minutes
Sleep consists of ~90-minute cycles of light sleep, deep sleep, and REM. Waking at the end of a cycle (rather than mid-cycle) helps you feel refreshed. Most adults need 5-6 complete cycles per night.
If you wake in the middle of a deep sleep phase (mid-cycle), you will feel groggy regardless of total sleep time. The key is completing full 90-minute cycles.
Most adults need 5-6 complete cycles (7.5-9 hours). Teenagers need 6 cycles (9 hours). Older adults may be fine with 5 cycles (7.5 hours).
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