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The 90-minute loop
Adults cycle through four sleep stages — N1, N2, N3 (deep), and REM — repeating roughly every 90 minutes throughout the night.
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SleepSync uses 90-minute sleep cycles and your age to recommend exactly when to sleep — or when to wake — so you rise sharp instead of groggy.
Your brain cycles through light, deep, and REM sleep — about every 90 minutes. Hover any result above to see that night drawn out below.
Sleep isn't a flat state — it's a structured journey. Each cycle takes you from light sleep down into deep sleep, then up into REM, and back. The math behind SleepSync follows the same pattern your brain does every night.
Adults cycle through four sleep stages — N1, N2, N3 (deep), and REM — repeating roughly every 90 minutes throughout the night.
Waking between cycles, in light sleep, feels effortless. Cutting deep sleep short is what causes that heavy, foggy feeling.
Deep sleep dominates the early night; REM dominates the late night. That's why losing the last two hours of sleep hurts so much.
Adults need 7.5–9 hours — that's 5 to 6 cycles. Below 4 cycles, recovery and cognitive performance noticeably suffer.
Small, consistent changes outperform any sleep tracker or supplement.
Wake at the same time daily — including weekends. Consistency is the strongest signal for your circadian rhythm.
Sunlight within an hour of waking sets your internal clock and makes falling asleep that night much easier.
Caffeine has a six-hour half-life. The afternoon coffee is still in your system at midnight.
18–20 °C, blackout curtains, and earplugs or white noise. Your bedroom should feel like a cave.
Or at least face-down across the room. Notifications and blue light wreck the start of your night.
A simple 20-minute routine — read, stretch, shower — tells your brain it's time to power down.
Cycle length varies — adults average 70 to 110 minutes. SleepSync uses 90 because it's the sweet-spot average for most adults.
The age panel uses the National Sleep Foundation's published age-based recommendations. As you change your age, SleepSync also tells you whether the bedtime you've selected matches that range.
14 minutes is the population average sleep latency. Faster than that often signals sleep deprivation; much slower can suggest anxiety or being under-tired. The slider lets you tune it to yourself.
Five to six is the sweet spot for adults. Teens often need six or more. If you can only fit four, choose four full cycles over a half-cycle — waking mid-cycle is what causes grogginess.
No. SleepSync is a planning tool, not a measurement tool. For chronic sleep issues, consult a sleep specialist or use a clinically validated device.