How to Calculate Sleep
What is Sleep?
The sleep calculator uses the science of sleep cycles to recommend optimal bedtimes. During sleep the brain cycles through stages roughly every 90 minutes: light sleep, deep sleep (slow-wave), and REM (Rapid Eye Movement). Waking mid-cycle causes grogginess; waking at the end of a cycle feels natural and refreshed.
Formula
Step-by-Step Guide
- 1Average sleep cycle = 90 minutes (can range 80–120 min)
- 2Average time to fall asleep = 14 minutes
- 3Bedtime = Wake time − (cycles × 90 min) − 14 min
- 45–6 cycles = 7.5–9 hours — the recommended range for adults
- 54 cycles (6 hours) is the minimum to maintain cognitive function
Worked Examples
Frequently Asked Questions
What is Sleep?
The sleep calculator uses the science of sleep cycles to recommend optimal bedtimes. During sleep the brain cycles through stages roughly every 90 minutes: light sleep, deep sleep (slow-wave), and REM (Rapid Eye Movement)
How accurate is the Sleep calculator?
The calculator uses the standard published formula for sleep. Results are accurate to the precision of the inputs you provide. For financial, medical, or legal decisions, always verify with a qualified professional.
What units does the Sleep calculator use?
This calculator works with inches, watts. You can enter values in the units shown — the calculator handles all conversions internally.
What formula does the Sleep calculator use?
The core formula is: Average sleep cycle = 90 minutes (can range 80–120 min). Each step in the calculation is shown so you can verify the result manually.
Ready to calculate? Try the free Sleep Calculator
Try it yourself →