Sleep Calculator
Find the optimal bedtime or wake‑up time based on 90‑minute sleep cycles to wake up feeling refreshed.
Enter values and click Calculate
Calculate Optimal Bedtime or Wake‑up Time Based on Sleep Cycles
The Sleep Calculator uses the average sleep cycle length of 90 minutes and the typical time to fall asleep (14 minutes) to recommend the best time to wake up or go to bed. Completing full cycles helps you wake up at the end of REM sleep, which is more refreshing.
Formula
\text{Target Time} = \text{Reference Time} \pm (\text{cycles} \times 90 + 14 \text{ min})
How to Use?
- Choose whether you want to find bedtime or wake‑up time.
- Enter your reference time (bedtime or wake‑up time).
- Select the number of sleep cycles (4–6).
- The calculator shows the target time and total sleep hours.
Worked Examples
If you go to bed at 22:00, when to wake after 5 cycles?
Given:inputs
calculateFor:wakeup
referenceHour:22
referenceMinute:0
sleepCycles:5
Result:calculated
timeStr:07:44
Sleep Cycles
A full sleep cycle lasts about 90 minutes. Waking at the end of a cycle leaves you more refreshed.
Fall‑Asleep Time
We add 14 minutes to account for the average time to fall asleep.
Table: Sleep Cycle Recommendations
| Cycles | Hours | Description |
|---|---|---|
| 4 | 6 | Minimum recommended |
| 5 | 7.5 | Ideal for most adults |
| 6 | 9 | Extra rest |
FAQs
Why 90 minutes?
A typical sleep cycle (light, deep, REM) lasts about 90 minutes.
What about the 14 minutes?
It takes most people around 14 minutes to fall asleep.