Sleep Cycles
Based on 90-minute sleep cycles, find ideal bedtimes and wake times.
Recommended bedtimes
12:45 AM
4 cycles
11:15 PM
5 cycles
9:45 PM
6 cycles
Sleep cycles are roughly 90 minutes each. Add 15 minutes for falling asleep. Choose the option that fits your schedule best.
A sleep calculator is a tool that computes recommended bedtimes or wake times based on sleep cycles—typically 90 minutes long. Each cycle progresses through light sleep, deep sleep, and REM sleep. By waking or sleeping for whole cycles (plus 15 minutes to fall asleep), you align your rest with your body's natural rhythms, promoting deeper, more restorative sleep.
Enter your desired wake time or bedtime. The calculator then works backwards or forwards in 90-minute increments, adding 15 minutes for sleep onset, to suggest three bedtime or wake-time options covering 4, 5, and 6 complete cycles (approximately 6, 7.5, and 9 hours of sleep). Choose the option that best fits your schedule and commitments.
Recommended bedtime = Wake time − (cycles × 90 min + 15 min fall-asleep time)
Recommended wake time = Bedtime + (cycles × 90 min + 15 min fall-asleep time)Each full sleep cycle lasts roughly 90 minutes. To this we add 15 minutes for sleep onset (the time it takes to fall asleep after closing your eyes). By calculating whole cycles, you avoid waking during vulnerable light-sleep phases where you'll feel groggy. If you want to wake at 07:00, subtract the total sleep time from that; if going to bed at 22:30, add the total to find your natural wake point.
| Input | Result | Notes |
|---|---|---|
| Want to wake at 07:00 AM, prefer 5 cycles | Bedtime: 11:15 PM (7.5 hours sleep + 15 min fall-asleep = 7 hours 45 min total) | Waking after 5 complete cycles helps you avoid mid-cycle grogginess. The 15-minute buffer accounts for typical time to fall asleep. |
| Going to bed at 23:00 (11 PM), want 6 cycles | Wake time: 08:30 AM (9 hours sleep + 15 min = 9 hours 15 min total) | Six cycles gives maximum rest; waking at 08:30 keeps you aligned with your cycle rhythm instead of fighting it. |
| Tight schedule: wake at 06:30 AM, minimum sleep needed | Bedtime: 11:45 PM (4 cycles = 6 hours + 15 min buffer) | Four cycles is the minimum for basic sleep maintenance. Though less than ideal, it's still better than waking mid-cycle. |
Sleep cycles average 90 minutes, but they range from 80–100 minutes depending on age, health, and individual variation. 90 is a reliable middle ground. If you consistently feel better with a slightly different cycle length, adjust by ±5–10 minutes and test.
If you fall asleep in 5 minutes, the 15-minute buffer is conservative and still works—you'll just have a bit of extra sleep. If you take 25+ minutes, the recommendation might wake you slightly early; adjust by adding 10 minutes to the suggested time.
This calculator is for night-time sleep. Daytime naps disrupt your main sleep cycle and are separate from your overnight sleep architecture. For naps, 20 minutes is ideal (not long enough to enter deep sleep) or a full 90-minute nap if you have time.
Yes, but the benefit is reduced because your body doesn't develop a consistent rhythm. Use the calculator to align each sleep block with cycles, but prioritise consistency above all—even shift workers do better with predictable sleep times relative to their shifts.
Brief awakenings are normal and often unremembered. If you're waking frequently, sleep quality may be affected by stress, caffeine, or environment—those are bigger issues than cycle timing. The calculator optimises *when* you sleep, not *how well* you sleep in poor conditions.
No. This calculator runs entirely in your browser and does not store, send, or log any of your data. Your sleep times are private to you.