Sleep Calculator – Best Bedtime & Wake-up Times
Choose a mode, set a time, and we’ll suggest times that land at the end of 90-minute sleep cycles (we add a small buffer for falling asleep).
Tip: People often feel best after 5–6 cycles (~7.5–9 hours). Your ideal may vary.
How it works
Sleep tends to occur in ~90-minute cycles. Waking up at the end of a cycle can feel easier than waking mid-cycle. This calculator adds a short buffer (default 14 minutes) for the time it typically takes to fall asleep, then suggests bedtimes or wake-up times that land near the end of cycles.
FAQ
What assumptions does this calculator use?
We use 90-minute cycles and a default 14-minute fall-asleep buffer. You can change the buffer to suit you.
How many cycles should I target?
Many adults prefer 5–6 cycles (about 7.5–9 hours), but sleep need is individual. Use these times as gentle suggestions.
Is my data private?
Yes. Everything runs locally in your browser; no data is uploaded.
Additional Information About Sleep Cycles
Human sleep is divided into repeating 90-minute cycles, consisting of light sleep, deep sleep, and REM (rapid eye movement) sleep. Waking up at the end of a cycle generally feels easier than waking up in the middle of one.
Typical Sleep Needs
- Adults: 7–9 hours (about 5–6 cycles)
- Teenagers: 8–10 hours (about 5–7 cycles)
- Children: 9–12 hours (about 6–8 cycles)
- Infants: 12–16 hours including naps
Why Sleep Quality Matters
Sleep isn’t just about quantity—it’s also about quality. Factors like screen time, caffeine, stress, and environment (light, noise, temperature) affect how restorative your sleep cycles are. Good “sleep hygiene” practices, such as keeping a consistent bedtime and limiting blue light before bed, help improve quality.
Limitations of This Calculator
This tool provides general suggestions based on average cycle lengths. Everyone’s sleep architecture is unique, and cycles may range from 80–110 minutes. For ongoing sleep issues, consult a healthcare professional.