Sleep Calculator – Find Your Ideal Bedtime in Seconds
The Sleep Calculator on Addition.site is a quick, free web‑app that tells you exactly when to go to bed so you can wake up refreshed.
By entering the time you plan to wake up and the number of full sleep cycles you want (6 – 8), the calculator works out the optimal bedtime based on the science of sleep cycles (≈ 90 minutes each) plus a 15‑minute “fall‑asleep” buffer.
How to Use the Calculator
- Enter Wake‑Up Time
- Click the clock field and pick the hour and minute you need to be up.
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The field accepts 24‑hour or 12‑hour formats (e.g., 07:30 AM or 19:30).
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Choose Sleep Cycles
- Spin the number box or type a value between 6 and 8.
- 6 cycles = 9 hours of sleep, 8 cycles = 12 hours.
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The default is 6 cycles, which most adults find comfortable.
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Calculate
- Hit the “calculate” button.
- The result appears in the read‑only input field below the calculator.
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Click the result to copy the bedtime to your clipboard – a quick “Copied!” message confirms it.
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Share Your Bedtime
- Tap the 𝕏 button to open a pre‑filled tweet with your bedtime, so you can share your new sleep routine on X (formerly Twitter).
What the Calculator Is Doing
- Sleep Cycle Length – 90 minutes (typical REM + deep sleep).
- Time to Fall Asleep – 15 minutes added to the total.
- Bedtime = Wake‑Up Time – (Cycles × 90 min + 15 min).
- The algorithm uses JavaScript’s
Dateobject to do the math, so the time shown respects the 24‑hour clock and daylight‑saving adjustments automatically.
Why Sleep Cycles Matter
- Quality Sleep – Waking at the end of a cycle reduces grogginess and improves alertness.
- Memory & Mood – Full cycles help consolidate memories and regulate emotions.
- Health Benefits – Consistent cycle‑aligned sleep lowers the risk of hypertension, obesity, and depression.
Use Cases
| Situation | How the Calculator Helps |
|---|---|
| Early‑Bird Work | Plan a bedtime that lets you wake up ready for a 6 AM meeting. |
| Night Shift | Adjust wake‑up time to the end of a cycle after a late shift. |
| Travel | Align sleep with new time zones by calculating the best bedtime before departure. |
| Fitness | Optimize recovery by ensuring you get a full number of cycles before training. |
| Sleep Coaching | Use as a teaching tool for clients on sleep hygiene. |
Additional Features
- Mobile‑Friendly – Responsive layout works on phones, tablets, and desktops.
- Copy to Clipboard – One click copies the bedtime for easy pasting into a calendar or notes app.
- Share on X – Built‑in tweet button to spread your new bedtime routine.
- No Personal Data – All calculations run locally in your browser; no tracking or data upload.
- Open Source – The code is freely available for anyone to inspect or modify.
Summary
- Sleep Calculator – Find Your Ideal Bedtime
- Use the free Sleep Calculator to calculate the perfect bedtime based on your wake‑up time and sleep cycles. Share on X and improve sleep quality.
- Try the sleep calculator. A bedtime calculator to find your optimal bedtime. Measure sleep cycles. Improve sleep hygiene, for overall better sleep, health, and general wellbeing.
Start planning better sleep today – just enter your wake‑up time, pick 6–8 cycles, and let the Sleep Calculator show you the ideal bedtime.