Sleep Calculator

Find the perfect bedtime or wake-up time aligned to your natural 90-minute sleep cycles.

Calculate Your Sleep

Wake-Up Time

We'll show you the best times to fall asleep tonight.

Time to Fall Asleep (sleep onset latency)

Age Group (affects recommended sleep duration)

Optimal Sleep & Wake Times

Sleep Cycle Breakdown

Sleep Quality Guide

🌙 Sleep Stages (per 90-min cycle)

Stage 1 (N1): ~5 min — Light sleep, easy to wake

Stage 2 (N2): ~25 min — Heart rate slows, body temp drops

Stage 3 (N3): ~30 min — Deep sleep, hardest to wake, restorative

REM Sleep: ~30 min — Dreaming, memory consolidation

✅ Sleep Hygiene Tips

• Keep the same sleep/wake time every day

• Avoid screens 30–60 min before bed

• Keep bedroom cool (65–68°F / 18–20°C)

• Avoid caffeine after 2pm

• No alcohol within 3 hours of bedtime

Recommended (Adults)

7–9 hrs

per NSF guidelines

Ideal Cycle Count

5–6 cycles

7.5–9 hours

Minimum (short-term)

4–5 cycles

6–7.5 hours

Sleep cycles: Your brain cycles through sleep stages approximately every 90 minutes. Waking up mid-cycle — especially during deep sleep (Stage 3) — causes that groggy, disoriented feeling called sleep inertia. Waking at the end of a complete cycle means you're in light sleep and wake up naturally refreshed.

REM rebound: REM sleep (dreaming, memory processing) happens predominantly in the later cycles. If you only sleep 4–5 hours, you miss most of your REM sleep regardless of when you go to bed. This is why "catching up on sleep" on weekends has limits — you can partially recover slow-wave sleep but cannot fully make up lost REM.

Sleep onset latency: The average person takes 10–20 minutes to fall asleep. If you fall asleep the moment your head hits the pillow, you may actually be significantly sleep deprived. A well-rested person typically takes 10–20 minutes.

⚠️ These times are based on average 90-minute sleep cycle research. Individual cycle length varies by 80–110 minutes. If you struggle with sleep, consult a physician or sleep specialist. Chronic sleep deprivation is linked to serious health conditions.