Loading...
Find bedtimes and wake times that land between 90-minute sleep cycles.
A sleep cycle is a ~90-minute progression through light sleep (N1, N2), deep sleep (N3), and REM sleep. Waking at the end of a complete cycle reduces grogginess and improves alertness.
⏱ Includes 15 min to fall asleep. 5-6 cycles (7.5-9h) recommended.
| Stage | Duration | Function |
|---|---|---|
| N1 (Light) | 5 to 10 min | Transition to sleep, easily awakened |
| N2 (Light) | 10 to 25 min | Body temperature drops, heart rate slows |
| N3 (Deep/SWS) | 20 to 40 min | Physical restoration, growth hormone release |
| REM | 10 to 60 min | Dreaming, memory consolidation, brain restoration |
Formula
Bedtime = Wake Time − (Cycles × 90 min) − 15 min (fall asleep time)Cycles = Number of complete sleep cycles (typically 4-6)
90 min = Average duration of one complete sleep cycle
15 min = Average time to fall asleep (sleep onset latency)
Worked Example
Wake at 7:00 AM, target 5 cycles
Did you know? The CDC reports that 1 in 3 American adults does not get enough sleep. Chronic sleep deprivation (< 7 hours) is associated with a 12% increase in all-cause mortality and significantly higher risks of obesity, diabetes, and cardiovascular disease (source: CDC).
Sources
Convert A1C to average glucose and back, with the full A1C chart and ADA bands.
Calculate BMR using 3 validated formulas. See daily calorie needs by activity level.
Estimate BAC using the Widmark formula. Enter drinks, weight, and hours to gauge impairment.
Predict a child's possible blood types from both parents, with probabilities.
Calculate BMI and see your weight category. Includes healthy weight range for your height.
Calculate body fat percentage using the US Navy method with simple body measurements.