Fitness & Health
Sleep Calculator
Find optimal bedtime and wake time by sleep cycles.
Inputs
Adjust the assumptions to match your scenario. Results update instantly.
Results
Primary outputs and comparison insights are built from the current inputs.
Bedtime (6 cycles)
21.75
Bedtime for 6 full sleep cycles (~9 hours).
Bedtime (5 cycles)
23.25
Bedtime for 5 full sleep cycles (~7.5 hours).
Bedtime (4 cycles)
0.75
Bedtime for 4 full sleep cycles (~6 hours).
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How this Sleep Calculator works
The Sleep Calculator suggests ideal bedtimes based on complete 90-minute sleep cycles so you wake between cycles and feel rested. Enter wake time (hour, 0-23), sleep cycle (minutes), and time to fall asleep (min) to estimate bedtime (6 cycles), bedtime (5 cycles), and bedtime (4 cycles). The calculator updates instantly and adds a comparison table plus chart so you can test the sensitivity of the result before you use it in a decision.
Quick guide
Jump to the section you need, then return to the sleep calculator.
Inputs
- Desired wake-up hour in 24-hour format.
- Length of one sleep cycle (typically 90 minutes).
- Average minutes needed to fall asleep.
Outputs
- Bedtime for 6 full sleep cycles (~9 hours).
- Bedtime for 5 full sleep cycles (~7.5 hours).
- Bedtime for 4 full sleep cycles (~6 hours).
Assumptions
- Average sleep cycle is 90 minutes.
- Waking between cycles reduces grogginess.
Tips
- Most adults need 5-6 cycles (7.5-9 hours).
- Keep a consistent schedule even on weekends.
Sleep Calculator formula guide
Use these sleep calculator formulas to audit the output or explain it to someone else.
1 formulas
Sleep Calculator examples
Review a ready-made sleep calculator scenario, copy it, then tweak inputs to match your case.
Example
Early riser plan
Inputs
- Example input Wake time (hour, 0-23): 6
- Example input Sleep cycle (minutes): 90
- Example input Time to fall asleep (min): 15
Outputs
- Example result Bedtime (6 cycles): 20.75
- Example result Bedtime (5 cycles): 22.25
- Example result Bedtime (4 cycles): 23.75
For a 6 AM wake time, going to bed at 9:15 PM or 10:45 PM completes full cycles.
Bedtime by wake time
| Wake time (hour, 0-23) | Bedtime (5 cycles) | Bedtime (6 cycles) |
|---|---|---|
| 5 | 21.25 | 19.75 |
| 6 | 22.25 | 20.75 |
| 7 | 23.25 | 21.75 |
| 8 | 0.25 | 22.75 |
| 9 | 1.25 | 23.75 |
Waking between sleep cycles leads to feeling more refreshed.
Bedtime suggestions
Focus point
5
21.25
Position
#1 of 5
Original order
Share of total
31.14%
Total: 68.25
Waking between sleep cycles leads to feeling more refreshed.
References
- Sleep cycle duration research
- National Sleep Foundation recommendations
Learn more
Guides connected to the sleep calculator
Use these short guides when you want the decision framework behind the numbers, not just the raw output.
Category guide
Fitness & Health Calculator Guide
Use body, nutrition, and training calculators as planning tools rather than diagnoses, and focus on trends instead of one-off numbers.
Directly related
Articles that mention this calculator
FAQ
Sleep Calculator FAQ
What does the Sleep Calculator do?
The Sleep Calculator suggests ideal bedtimes based on complete 90-minute sleep cycles so you wake between cycles and feel rested. Enter wake time (hour, 0-23), sleep cycle (minutes), and time to fall asleep (min) to estimate bedtime (6 cycles), bedtime (5 cycles), and bedtime (4 cycles). The calculator updates instantly and adds a comparison table plus chart so you can test the sensitivity of the result before you use it in a decision. It is part of our fitness & health toolkit.
What inputs do I need?
Typical inputs include Desired wake-up hour in 24-hour format., Length of one sleep cycle (typically 90 minutes)., Average minutes needed to fall asleep..
How are the results calculated?
We follow the formulas and assumptions outlined in the "How this calculator works" section. You will see outputs like Bedtime for 6 full sleep cycles (~9 hours)., Bedtime for 5 full sleep cycles (~7.5 hours)., Bedtime for 4 full sleep cycles (~6 hours)..
Can I share or download the results?
Use the Copy link or Print buttons to share your results. If a table or chart appears, you can download the data as CSV.
Is my data stored?
No. Calculations run in your browser and we do not store your inputs.
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