Calculate your perfect bedtime or wake-up time based on 90-minute sleep cycles — the science behind waking up naturally refreshed, without grogginess.
Your time: —
I want to wake up at…
I'm going to bed at…
Going to sleep right now?
We'll calculate your optimal wake times starting from this moment.
💡 Good to know: We account for 15 minutes to fall asleep. Each recommended time represents waking at the natural end of a complete 90-minute sleep cycle.
Your Sleep Architecture
How a single 90-minute cycle moves through sleep stages
N1
N2
N3
REM
N1
N2
N3
REM
N1 — Light
N2 — Light
N3 — Deep
REM
Two cycles shown above. A full night of rest = 5–6 cycles (7.5–9 hours)
How It Works
Three simple steps to your most restorative sleep
1
Enter Your Time
Tell us your wake-up time, your planned bedtime, or tap "right now" to calculate from this exact moment.
2
We Do the Science
We add 15 minutes to fall asleep, then map complete 90-minute cycles to find your ideal sleep and wake windows.
3
Wake Up Refreshed
Set your alarm to one of the recommended times. You'll surface naturally at the lightest point of your sleep cycle.
Sleep Optimization Tips
Science-backed habits for deeper, more restorative rest
1
Consistent Schedule
Go to bed and wake at the same time every day — even weekends. Regularity anchors your circadian rhythm and improves sleep quality over time.
2
Cool, Dark Environment
Your core body temperature drops during sleep. Keep your bedroom at 65–68°F (18–20°C) and block out light for optimal deep sleep.
3
Digital Detox
Blue light from screens suppresses melatonin production. Put devices away at least 60 minutes before your bedtime for faster sleep onset.
4
Caffeine Cutoff
Caffeine has a half-life of ~5 hours. Stop consuming it by early afternoon to prevent disrupted deep sleep (N3) later that night.
Frequently Asked Questions
Everything you need to know about sleep cycles and this calculator
Our sleep calculator uses the science of 90-minute sleep cycles. It adds 15 minutes (the average time to fall asleep) to your bedtime, then calculates exactly when you complete 5 or 6 full cycles — giving you the best times to wake up feeling truly refreshed, not groggy and disoriented.
Most adults need 7–9 hours per night, which equals 5–6 complete 90-minute sleep cycles. Teenagers need 8–10 hours, while school-age children need 9–11 hours. Most people who feel they "only need 5 hours" are actually building a sleep debt that impairs cognition, mood, and health over time.
Grogginess (called sleep inertia) occurs when you're woken mid-cycle during deep sleep (N3 stage). Your brain is in maximum restorative mode and resists abrupt waking. Even 8 hours of sleep can leave you feeling awful if your alarm interrupts a deep phase. Our calculator times your wake-up to the lightest phase at the natural end of a cycle.
Each 90-minute cycle has four stages: N1 (light sleep, 1–7 min — you drift off), N2 (light sleep, 10–25 min — body temperature drops, heart rate slows), N3 (deep/slow-wave sleep — the most physically restorative phase, hardest to wake from), and REM (Rapid Eye Movement — vivid dreaming, memory consolidation, and emotional processing). Early-night cycles have more N3; later cycles have more REM.
Absolutely! For power naps, aim for 20 minutes (this prevents entering deep sleep and keeps you alert afterward) or a full 90-minute cycle (one complete cycle for deeper restoration). Use the "right now" button and look at the first result for a single-cycle nap. Avoid napping after 3 PM as it can delay your nighttime sleep onset.
Sleep cycles average 90 minutes but naturally range from 80–110 minutes depending on the individual, age, health, and stage of the night. The calculator uses 90 minutes as a scientifically validated average. For most people this is accurate within 10–15 minutes — close enough to meaningfully reduce morning grogginess and improve how you feel each day.