Sleep Calculator
Find the perfect bedtime or wake time based on 90-minute sleep cycles. Wake up at the end of a cycle to feel refreshed — not groggy.
CL
CalcLeap Editorial Team
Reviewed by certified professionals · Last updated April 1, 2026
Plan Your Sleep
Understanding Sleep Cycles
| Cycles | Duration | Quality |
|---|---|---|
| 6 cycles | 9 hours | Excellent — maximum recovery |
| 5 cycles | 7.5 hours | Ideal — recommended for most adults |
| 4 cycles | 6 hours | Adequate — minimum for function |
| 3 cycles | 4.5 hours | Short — use only when necessary |
Each sleep cycle lasts ~90 minutes and includes light sleep, deep sleep, and REM. Waking between cycles (not mid-cycle) is the key to feeling refreshed.
Related Tools
📐 How We Calculate This
Our calculations follow clinical guidelines from the CDC, WHO, and NIH. BMI uses the standard formula: weight (kg) / height (m²). Caloric estimates use the Mifflin-St Jeor equation, validated as the most accurate resting metabolic rate formula.
These tools are for informational purposes and do not replace medical advice. Consult a healthcare provider for personalized health recommendations.
📚 Sources & References
Frequently Asked Questions
Why do I feel groggy when I wake up?
You're likely waking up in the middle of a deep sleep cycle. By timing your wake-up to the end of a 90-minute cycle, you wake during lighter sleep and feel much more alert.
How long does it take to fall asleep?
On average, it takes about 15 minutes to fall asleep. This calculator accounts for that by adding 15 minutes to your target bedtime.
How many hours of sleep do adults need?
Most adults need 7–9 hours (5–6 sleep cycles). Some people function well on 6 hours, while others need 9. Consistent sleep quality matters more than exact hours.