Sleep Calculator
Estimate a possible bedtime or wake-up time, based on an approximate sleep cycle average — not a personalised measurement.
This calculator provides a general estimate for informational purposes only. It is not a medical device and does not provide medical advice or diagnosis. Always consult a qualified healthcare professional about your individual health circumstances.
Frequently Asked Questions
Why 90-minute cycles?
Sleep happens in cycles, moving through light, deep and REM sleep — 90 minutes is a commonly-cited average, though real cycles range from about 70 to 120 minutes and tend to lengthen later in the night. This calculator is a popular heuristic based on that average, not a personalised measurement of your own cycles (which would need actual sleep tracking). Waking up near the end of a cycle rather than in the middle of one tends to leave people feeling more refreshed.
What's the 15-minute buffer for?
It's a general allowance for the time it typically takes to fall asleep after getting into bed, so the bedtime suggestions reflect when to actually turn the lights off.
How many cycles should I aim for?
Most adults need 5–6 complete cycles (about 7.5–9 hours) per night. Fewer than 4 cycles regularly is generally considered insufficient sleep for most adults.
Want lab-grade insight to go with this estimate?
Wellness
