Sleep Cycle Calculator
Find optimal sleep and wake times based on 90-minute sleep cycles.
14 min
5 min (fast sleeper)45 min (slow sleeper)
🌙 Enter your bedtime to find optimal wake-up times
Based on 90-minute sleep cycles + sleep onset delay
About Sleep Cycle Calculator
Free online sleep cycle calculator based on 90-minute sleep cycles. Find the best wake-up times or bedtimes to avoid grogginess. Includes nap calculator, sleep debt tracker, sleep quality tips, chronotype detection, and sleep stage breakdown.
How to Use
- 1Choose "I go to bed at…" or "I want to wake at…" mode.
- 2Enter your bedtime or desired wake-up time.
- 3Adjust the slider for how long it takes you to fall asleep.
- 4Click Calculate to see 4 optimal times (4–7 cycles).
- 5Green cards (5–6 cycles) are the recommended target.
- 6Use the Nap Calculator to plan restorative naps.
- 7Expand Sleep Debt to track your weekly deficit.
- 8Expand Sleep Quality Tips for science-backed sleep advice.
Frequently Asked Questions
How does the sleep cycle calculator work?
Human sleep consists of 90-minute cycles. Waking up at the end of a cycle (in light sleep) means you feel refreshed. The calculator adds your sleep onset delay to your bedtime and shows wake-up times at 4, 5, 6, and 7 cycle intervals.
How many sleep cycles should I get?
5–6 cycles (7.5–9 hours) is ideal for most adults. 4 cycles (6 hours) is the minimum for cognitive function.
What is sleep onset latency?
Sleep onset latency is the time it takes to fall asleep after going to bed. The average is 10–20 minutes. Adjust the slider to match your pattern.
What is sleep debt?
Sleep debt accumulates when you consistently sleep less than recommended (7–9 hours for adults). The Sleep Debt Calculator shows your daily and weekly deficit and recovery estimate.
What is the best nap length?
A 10–20 minute power nap boosts alertness without grogginess. A 90-minute nap completes a full sleep cycle. Avoid 30–60 minute naps — they enter deep sleep and cause grogginess.
What is a chronotype?
A chronotype is your natural sleep-wake preference. Larks prefer early schedules, owls are naturally alert in the evening. Chronotypes are largely genetic.
Tool Info
- Category
- health
- Usage
- Unlimited