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Sleep Calculator
Find your ideal bedtime and wake-up windows so you wake in lighter sleep stages.
Current time: 18:48
System will calculate ideal bedtimes
How This Sleep Calculator Works
Your sleep is not a single block of rest. Every night your brain moves through repeating 90-minute sleep cycles, each including light sleep, consolidated sleep, deep slow-wave sleep, and REM. A strong sleep calculator helps you wake near cycle boundaries instead of in deep sleep, reducing morning grogginess.
This sleep calculator works in three steps. First, enter when you need to wake up or when you plan to sleep. Second, set your normal sleep onset delay, usually around 15 minutes. Third, choose your age group so recommendations align with guideline ranges. You then get practical bedtime or wake-up options based on completed cycles rather than arbitrary hour targets.
Use the sleep calculator tool for full control, the bedtime calculator when you know your alarm time, and the nap calculator for daytime recovery.
Recommended sleep by age
Source: CDC / AASM guidance
| Age group | Recommended sleep | Typical cycles | Notes |
|---|---|---|---|
| 0-3 months | 14-17 h | 9-11 | Includes daytime naps |
| 4-11 months | 12-15 h | 8-10 | Multiple naps |
| 1-2 years | 11-14 h | 7-9 | Includes naps |
| 3-5 years | 10-13 h | 6-8 | Includes naps |
| 6-12 years | 9-12 h | 6-8 | Continuous night sleep |
| 13-17 years | 8-10 h | 5-6 | Later chronotype common |
| 18-64 years | 7-9 h | 5-6 | Core recovery window |
| 65+ years | 7-8 h | 5 | Deep sleep share declines |
What Happens in Each Sleep Stage
Understanding sleep stages makes every recommendation from a sleep calculator more useful.
N1 - Light Sleep (5-10 min)
This is the transition into sleep. You can wake easily and usually feel clear-headed. The sleep calculator aims wake suggestions near this lighter transition point.
N2 - Sleep Consolidation
Heart rate slows, body temperature drops, and memory processing starts. N2 is often the largest share of a typical night and supports stable sleep continuity.
N3 - Deep Slow-Wave Sleep
Physical repair peaks here. Waking in N3 can trigger strong sleep inertia, the heavy and disoriented feeling many people experience after an alarm.
REM - Rapid Eye Movement
REM supports emotional processing and creative integration. Late-night REM periods get longer, so very short nights often sacrifice REM first. Read the full sleep stages guide for deeper details.
Science-backed sleep quality tips
Small habits create large gains in recovery.
No screens 1h before bed
Blue light delays melatonin and shifts your biological night.
Keep wake time fixed
A stable wake time is the fastest way to stabilize circadian rhythm.
Stop caffeine after 2 PM
Caffeine half-life can still disturb deep sleep late at night.
Warm shower before bed
Post-shower cooling supports natural sleep pressure.
Get morning sunlight
10 minutes of daylight helps anchor your internal clock.
Frequently Asked Questions
Is the sleep calculator accurate?
The calculator uses the accepted 90-minute cycle average from sleep research. Individual cycles can vary, so treat results as a precise starting point and adjust by one cycle if needed.
Why do I feel worse after 9 hours than after 7.5?
Total hours are only part of sleep quality. If your alarm interrupts deep sleep, sleep inertia can feel stronger than after a shorter but better-timed night.
Can shift workers use this sleep calculator?
Yes. Enter your real planned sleep or wake time, whether day or night. The sleep calculator works from cycle timing, not fixed clock-hour assumptions.
How is the bedtime calculator different from the sleep calculator?
The bedtime calculator focuses on reversing a wake time into a bedtime. The main sleep calculator supports all three planning modes with the same cycle logic.