Compare Bedtimes by Fixed Sleep Blocks
Compare candidate bedtimes by dividing sleep into fixed 90-minute blocks. This is a clock-planning exercise without brain-wave measurement or actual sleep-stage detection.
- Runs in your browser
- Nothing is uploaded
- No signup; device limits apply
Numbers stay on your device. Nothing is sent to a server.
Time in bed before sleep is assumed to start. 14–20 minutes is a common pad.
How to use this tool
Choose wake time and assumed minutes to fall asleep. Sleep onset itself varies, so treat the allowance as planning room rather than a measurement guaranteed to repeat every night.
Results and examples
Read total duration alongside the headline and alternative blocks. Given NHLBI’s described 80–100-minute variation, a minute-specific bedtime cannot reliably align waking with an actual stage boundary.
Worked example
Waking at 06:30 with 20 minutes to fall asleep and five blocks gives a previous-day bedtime of 22:40.
Limitations
- Wearable data, awakenings and naps are not modelled.
- Short-duration candidates are not recommendations for sufficient sleep.
Fields
| Field | Guidance and constraints |
|---|---|
| Wake-up time | Check the unit and format displayed beside this field. |
| Minutes to fall asleep | Time in bed before sleep is assumed to start. 14–20 minutes is a common pad. · Accepted range: 0–90 · Input step: 1 |
Data handling
Processing stays in the current browser tab; the site does not upload tool input for the calculation itself.
Sources
Frequently asked questions
Can onset be zero?
Arithmetically yes, but that assumes falling asleep immediately.
Does it wake me at the end of REM?
No. It does not detect sleep stages.
Related tools
You do not need to start over. Continue with the tool that fits your next step.
