Sleep Cycle Calculator 2025

Sleep Cycle Calculator: Best Bedtime & Wake-Up Time in 2025

Wake up refreshed — not groggy. Our sleep cycle calculator uses 90-minute cycles to find the perfect bedtime or wake-up time so you finish a cycle, not interrupt REM.

How Sleep Cycles Work

One cycle = 90 minutes:

Stage 1: Light sleep (5–10 min)
Stage 2: Body prep (20 min)
Stage 3: Deep sleep (20–30 min)
REM: Dream sleep (10–30 min)

Wake at end of cycle = alert. Wake mid-cycle = groggy.

Formula

Bedtime = Wake-up − (Cycles × 90 min) − Fall-asleep time
Wake-up = Bedtime + (Cycles × 90 min) + Fall-asleep time
Cycles: 4–6 (6–9 hrs total)

Example: Wake at 7:00 AM, 15 min to fall asleep

6 cycles: 7:00 − 9 hrs − 15 min = 9:45 PM
5 cycles: 7:00 − 7.5 hrs − 15 min = 11:15 PM
4 cycles: 7:00 − 6 hrs − 15 min = 12:45 AM

Recommended Sleep by Age

Age	Hours	Cycles
0–3 months	14–17	9–11
4–11 months	12–15	8–10
1–2 years	11–14	7–9
3–5 years	10–13	7–9
6–13 years	9–11	6–7
14–17 years	8–10	5–7
18–64 years	7–9	5–6
65+ years	7–8	5

Sleep Debt

1 hr short = 1 coffee to recover
5+ hrs/week = impaired cognition
Catch-up: Sleep in on weekends (max 1 hr extra)

Pro Tips

Stick to same bedtime ±30 min
Avoid screens 1 hr before bed
Keep room 60–67°F
Use white noise
No caffeine after 2 PM

Common Myths

8 hrs for all? No — 7–9 range
Naps hurt night sleep? Only if >30 min or after 3 PM
Alcohol helps sleep? Fragments REM

Tools

Sleep tracker (Oura, Fitbit)
Blue-light glasses
Weighted blanket
Smart alarm (sunrise simulation)

Related Calculators

FAQs

How many cycles should I get? 5–6 (7.5–9 hrs).

Is 6 hours enough? Only for rare "short sleepers" (genetic).

Best nap length? 20 min (Stage 2) or 90 min (full cycle).

Can I train 6 hrs? Not safely — leads to health risks.

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