Sleep Cycle Calculator

Find optimal bedtime and wake time by 90-minute sleep cycles

Updated June 25, 2026

What is the Sleep Cycle Calculator?

Find your ideal bedtime or wake-up time based on natural 90-minute sleep cycles. Wake up feeling refreshed by aligning with your body's rhythms instead of fighting them. Why it matters: Most people feel groggy because they wake mid-cycle. This tool calculates multiple optimal options (4-6+ cycles) plus 15-minute sleep latency so you can plan better sleep.

Sleep occurs in repeating ~ 90-minute cycles (light \to deep \to REM). Adults typically need 4-6 cycles per night (6-9 hours total). The Math Target time (wake or bed) + sleep latency (default 15 min to fall asleep) Subtract/add full cycles (90 min each) Multiple recommendations shown for flexibility Modes Wake Time mode : Enter desired wake-up \to get best bedtimes Bedtime mode : Enter bedtime \to get best wake times Advanced : Customize cycle counts (e.g., 5,6,7). Results update live. All calculations run in your browser.

Calculate best bedtimes for refreshing sleep

7:00 AM (Wake Time mode)

Recommended bedtimes: 10:30 PM (5 cycles), 11:30 PM (6 cycles)

Find ideal wake times

11:00 PM (Bedtime mode)

Recommended wake times: 6:45 AM (5 cycles), 8:15 AM (6 cycles)

What is a sleep cycle?

A sleep cycle is a roughly 90-minute progression through light sleep, deep sleep, and REM stages. Most people go through 4-6 cycles nightly.

How long should I sleep?

Adults generally need 7-9 hours (about 5 cycles). This tool helps you hit complete cycles for better rest and easier waking.

What is sleep latency?

The time it takes to fall asleep after getting in bed — typically 10-20 minutes. We use 15 minutes by default.

Why do I feel groggy after 8 hours of sleep?

You likely woke in the middle of a deep sleep cycle. This calculator helps you time sleep to end on a lighter stage.

Can I use custom cycle numbers?

Yes. Toggle Advanced options and enter comma-separated values like 4,5,6,7 .

Does it account for time zones or DST?

No — it works with local clock times you provide. Use consistent daily schedules for best results.

Is 90 minutes the exact cycle length?

Average cycle is 90 minutes, but they vary (70-120 min). The tool uses the standard 90 min for reliable planning.

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