Sleep Calculator
Calculate the best bedtime or wake-up time based on 90-minute REM sleep cycles. Wake feeling refreshed, not groggy.
😴Sleep Calculator
I want to wake up at…
🌙When should I go to bed?
Pick the bedtime that works for you — each option completes a full sleep cycle (includes ~14 min to fall asleep).
💡 Amber = optimal. 5–6 cycles (7.5–9 hours) is the sweet spot for most adults. Waking mid-cycle causes grogginess (sleep inertia).
💤Sleep Quality Tips
Keep it cool
Your bedroom should be 60–67°F (15–19°C). Core body temperature drops during sleep, and a cooler room helps.
Screen-free 30 min before bed
Blue light suppresses melatonin. Put your phone down 30 minutes before your target bedtime.
Get morning sunlight
Exposure to natural light within an hour of waking anchors your circadian rhythm and boosts daytime alertness.
Consistent schedule
Going to bed and waking at the same time — even on weekends — is the #1 predictor of sleep quality.
Avoid alcohol before bed
Alcohol may help you fall asleep faster but it fragments REM sleep, leaving you groggy even after 8 hours.
Wind-down routine
A simple 20-minute routine (reading, stretching, journaling) signals to your brain that sleep is coming.
🔬How Sleep Cycles Work
Sleep happens in roughly 90-minute cycles. Each cycle moves through light sleep (N1/N2), deep slow-wave sleep (N3), and REM (Rapid Eye Movement) — the dreaming stage critical for memory consolidation and emotional regulation.
Waking at the end of a cycle means you surface naturally from light sleep, feeling alert and refreshed. Waking in the middle of a cycle — especially during deep sleep — triggers sleep inertia: that disoriented, groggy feeling that can last 30–60 minutes.
This calculator adds a 14-minute fall-asleep buffer (the average sleep-onset latency for healthy adults) so your alarm syncs perfectly with the end of a cycle.