Sleep Calculator

Find the perfect bedtime or wake-up time based on 90-minute sleep cycles. Wake up refreshed, not groggy.

Wake-up Time

Go to bed at...

2:16 AM

3 sleep cycles · 4.5h sleep

Minimum

12:46 AM

4 sleep cycles · 6h sleep

Short

11:16 PM

5 sleep cycles · 7.5h sleep

👍 Good

9:46 PM

6 sleep cycles · 9h sleep

✨ Optimal

Times account for ~14 minutes to fall asleep. Each sleep cycle is 90 minutes.

Why Sleep Cycles Matter

The 90-Minute Cycle

Each sleep cycle lasts approximately 90 minutes and consists of 4 stages: light sleep (N1), deeper sleep (N2), deep sleep (N3), and REM sleep. Waking up mid-cycle causes sleep inertia — that groggy, disoriented feeling.

By timing your wake-up to the end of a complete cycle, you wake during the lightest stage of sleep and feel naturally refreshed.

How Many Cycles Do You Need?

3 cycles (4.5h)Absolute minimum — not sustainable

4 cycles (6h)Short sleep — may impair performance

5 cycles (7.5h)Good — recommended for most adults

6 cycles (9h)Optimal — ideal for recovery days

Medium Rectangle (300×250)