Health calculator
Sleep Calculator
Find bedtimes or wake times based on 90-minute sleep cycles.
Formula
Sleep cycle estimate
Bedtime = wake time - sleep cycles x 90 minutes
For 5 cycles before 7:00 AM, bedtime is about 11:30 PM.
FAQs
Why 90-minute cycles?+
Sleep cycles are often approximated at about 90 minutes, though real sleep varies.
How does the Sleep Calculator calculate the result?+
It uses the Sleep cycle estimate: Bedtime = wake time - sleep cycles x 90 minutes. For 5 cycles before 7:00 AM, bedtime is about 11:30 PM.
What information do I need to use the Sleep Calculator?+
Find bedtimes or wake times based on 90-minute sleep cycles.
How accurate is the Sleep Calculator?+
Sleep Calculator applies the formula and assumptions shown on this page. Results may be rounded for readability, so verify changing rates, thresholds, medical guidance, or legal rules with the cited source or a qualified professional.
What should I check before using the Sleep Calculator result?+
Check that the units, dates, rates, and assumptions match your situation. Change one input at a time to understand which values have the largest effect on the result.
Health guide
How to use the Sleep Calculator
Find bedtimes or wake times based on 90-minute sleep cycles. The page also explains the sleep cycle estimate and shows a practical example: For 5 cycles before 7:00 AM, bedtime is about 11:30 PM.
- 1
Enter your details
Enter the values for the sleep calculator scenario you want to check.
- 2
Check the calculation
Review the result alongside the sleep cycle estimate: Bedtime = wake time - sleep cycles x 90 minutes.
- 3
Compare scenarios
Change one or more inputs to see how they affect the sleep Calculator result before you use the estimate.
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