Sleep Calculator

Find the ideal bedtime to complete full sleep cycles before your wake time.

Your Results

6 cycles (9h sleep)9:30 PM

5 cycles (7.5h sleep)11:00 PM

4 cycles (6h sleep)12:30 AM

Waking at the end of a 90-min cycle reduces grogginess.

Sleep runs in ~90-minute cycles through light, deep, and REM stages. Waking mid-cycle causes sleep inertia; waking at cycle end feels natural.

Most adults need 5-6 full cycles (7.5-9 hours). Four cycles works for some, but most people feel best at 7.5+ hours.