Health & Fitness

Sleep Calculator – 90-Minute Sleep Cycle Optimizer

Wake up refreshed between 90-minute REM cycles. Calculate the best bedtime or wake-up time without sleep inertia.

Health & Fitness ✓ Free & Instant

Wake up refreshed between 90-minute REM cycles. Calculate the best bedtime or wake-up time without sleep inertia.

Desired Wake-Up Time

Desired Bedtime

Going to sleep right now? We'll calculate the best times to set your alarm so you wake up feeling completely energized.

Average Time to Fall Asleep

5 min 14 min (avg) 20 min 30 min

Calculated Results ● Live

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Enter your values on the left and click Calculate to view instant results.

How to Use This Sleep Calculator

Choose your mode: “I want to wake up at…”, “I want to go to bed at…”, or “Sleep NOW”.
Set your target time and select your average time to fall asleep (5 to 30 mins).
Click Calculate Sleep Times to view optimal green-highlighted 5 to 6 cycle windows.

Human sleep naturally cycles every 90 minutes through NREM and REM stages:

Optimal Bedtime = Wake Time – (Cycles × 90 min) – Sleep Latency (avg. 14 min)

Waking up in light sleep rather than deep NREM stage 3/4 prevents sleep inertia, leaving you feeling energized.

Most healthy adults function best on 5 to 6 complete cycles (7.5 to 9 hours of sleep).