What is calculated
A bedtime from a user-selected wake time and sleep-duration target.
Sleep Calculator
Suggested bedtime
Enter your values, then calculate to see a verified result.
Reference range
How this result is calculated
A clear calculation path based on your inputs.
Inputs usedReview the information used for this result.
Full calculation and sourcesOpen Full calculation and sources to review the formula, assumptions, boundaries, and evidence.
Versioned calculationFormula v1.0.1
Method
Subtract the target and settling allowance, then wrap across midnight.
Important boundary
Actual sleep onset, awakenings, shift work, illness, and sleep quality are not predicted.
Set wake timeUse the labeled input and matching unit.
Measured or label valueSubtract the targetThe calculator applies the stated equation.
Full precision firstUse the scheduleKeep the boundary beside the result.
Reference, not diagnosisInterpretation
is the calculated bedtime.
The planned time in bed remains visible.
Persistent sleep difficulty needs appropriate professional evaluation.
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Method and test recordFormula v1.0.1
- Recorded scope
- health-wellness-completion
- Publisher
- CalculatorGeek
- Recorded review date
- 2026-10-05
- Next source review
- 2027-04-05
- Definition fixtures
- 2 configured scenarios
- Published examples
- 2 shown below
Recorded method
Recompute clock subtraction and midnight wrapping and inspect the formatted clock result.
These records describe the published model and reference tests. A test-case count is not a certification of every possible input or an independent specialist review. Editorial policy
Known limitations
- Uses a user-selected target rather than diagnosing sleep need.
- Does not predict sleep onset or sleep quality.
- Does not model naps, shift rotation, time-zone change, or interrupted sleep.
Method sources
Latest model update
2026-10-05 - Initial evidence-limited shared-system implementation with fixtures, original support content, and contextual links.
Reference inputs and expected results
Up to 12 examples from the configured definition fixtures are shown. Expected values use the stated output units; invalid inputs are intended to be rejected.
| Case | Inputs | Expected result |
|---|---|---|
| bedtime across midnight | Planned wake time (24-hour decimal): 7 h; Sleep target: 8 h; Time allowed to fall asleep: 0.25 h | bedtime_hours: 22.75; Suggested bedtime: 1365; Planned time in bed: 8.25 h (allowed numeric tolerance: 0.0001) |
| late wake reference | Planned wake time (24-hour decimal): 10 h; Sleep target: 7.5 h; Time allowed to fall asleep: 0.5 h | bedtime_hours: 2; Suggested bedtime: 120 (allowed numeric tolerance: 0.0001) |
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On this page
What the Sleep Calculator calculates
Calculate a clock bedtime from a wake time, sleep target, and allowance for falling asleep.
The target remains user-selected so the calculator does not pretend that one duration fits every age, schedule, or health situation.
Continue this workflow with the PHQ-9 Depression Screening. Calculate the public screening total with item 9 separate.
How to use the Sleep Calculator
- Enter the planned wake time as a 24-hour decimal.
- Choose a sleep-duration target.
- Add a realistic settling allowance.
- Review the result as a schedule anchor, not a promise of sleep.
Continue with the Sleep Debt Calculator. Compare recent sleep with a chosen nightly target.
Formula, variables and calculation order
bedtime = wake time - sleep target - settling time; add 24 hours when the result crosses midnight.
Inputs are validated and normalized before calculation. Full precision is retained until the displayed result is rounded.
Cross-check a different part of the decision with the Sleep Efficiency Calculator. Separate time asleep from time in bed.
Worked example and boundary check
Worked example
A 07:00 wake time, 8-hour target, and 15-minute allowance returns 22:45.
Boundary check
A 24-hour clock wraps at midnight; the calculation does not infer naps or awakenings.
How to interpret the result
Use the result to plan a consistent opportunity for sleep. Daytime sleepiness, loud snoring, breathing pauses, or ongoing insomnia need appropriate care.
- Uses a user-selected target rather than diagnosing sleep need.
- Does not predict sleep onset or sleep quality.
- Does not model naps, shift rotation, time-zone change, or interrupted sleep.
For a separate result with different assumptions, open the Caffeine Half-Life Calculator. Model a user-selected caffeine elimination scenario.
Frequently asked questions
Why is the target adjustable?
Sleep needs vary by age and person; CDC guidance should be read with individual circumstances.
Does this use 90-minute cycles?
No. Fixed cycle-count claims can create false precision because sleep cycles vary.
Can I enter 6:30?
Enter 6.5 for 06:30 in the current shared numeric input.
Will this cure insomnia?
No. It only performs schedule arithmetic.
Primary sources and evidence limits
Sources were checked 2026-10-05. A reference value, conversion, or schedule estimate is not a diagnosis, prescription, individualized treatment target, or substitute for professional care.