What This Calculator Measures

The Sleep Calculator determines your optimal bedtime based on when you need to wake up and how many complete sleep cycles you want. Waking up at the end of a complete sleep cycle (rather than in the middle of one) helps you feel more rested and alert.

Diagram showing how the Sleep Calculator works — How the Sleep Calculator works

How It Works

Each sleep cycle lasts approximately **90 minutes** and includes stages of light sleep, deep sleep, and REM sleep. The calculator works backward from your wake time:

**Bedtime = Wake Time - (Cycles x 90 min) - 15 min (to fall asleep)**

Cycles	Total Sleep	Bedtime for 6 AM wake
4 cycles	6 hours	11:45 PM
5 cycles	7.5 hours	10:15 PM
6 cycles	9 hours	8:45 PM

How Much Sleep Do You Need?

Most adults need 7-9 hours of sleep. For lifters, sleep is when the majority of muscle recovery and growth hormone release occurs:

•**Minimum for health:** 6 hours (4 cycles)

•**Recommended for most adults:** 7.5 hours (5 cycles)

•**Optimal for recovery:** 9 hours (6 cycles)

Research shows that sleeping less than 6 hours per night reduces testosterone levels by 10-15% and significantly impairs recovery from resistance training.

Limitations

•Sleep cycles vary in duration between individuals and even throughout the night (earlier cycles have more deep sleep, later cycles have more REM).

•The 90-minute cycle is an average. Individual cycle length ranges from 80-120 minutes.

•Sleep quality matters as much as quantity. A dark, cool room (18-20 degrees C) and consistent schedule are essential.