Sleep Cycle Calculator
Bedtimes that let you wake between cycles, not mid-cycle.
Enter your values
Enter the wake-up time (24h clock) in e.g. 6.5 = 06:30.
Enter the minutes to fall asleep in min.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Best bedtime (6 cycles, 9 h)
- 21:15
- Good bedtime (5 cycles, 7.5 h)
- 22:45
- Minimum (4 cycles, 6 h)
- 00:15
| Cycles | Sleep length | Go to bed at |
|---|---|---|
| 6 | 9 h | 21:15 |
| 5 | 7.5 h | 22:45 |
| 4 | 6 h | 00:15 |
| 3 | 4.5 h | 01:45 |
Quick answer
Sleep runs in roughly 90-minute cycles, so waking at the end of a cycle — after 5 or 6 cycles — feels far better than waking mid-cycle.
Sleep time = 90 min × cycles + 15 min to fall asleep
At a glance
| What it does | Bedtimes that let you wake between cycles, not mid-cycle. |
|---|---|
| Category | Health |
| Inputs needed | Wake-up time (24h clock), Minutes to fall asleep |
| Main output | Best bedtime (6 cycles, 9 h) |
| Formula | Sleep time = 90 min × cycles + 15 min to fall asleep |
| Cost | Free — no sign-up, no download |
How to use the Sleep Cycle Calculator
- 1Enter your wake time as a decimal hour, e.g. 6.5 for 06:30.
- 2Adjust how long you take to fall asleep.
- 3Pick a bedtime from the table.
Inputs explained
- Wake-up time (24h clock)(e.g. 6.5 = 06:30)
- Enter the wake-up time (24h clock) in e.g. 6.5 = 06:30.
- Minutes to fall asleep(min)
- Enter the minutes to fall asleep in min.
Worked example
Using the values the calculator loads with:
Inputs
- Wake-up time (24h clock)6.5 e.g. 6.5 = 06:30
- Minutes to fall asleep15 min
Results
- Best bedtime (6 cycles, 9 h)21:15
- Good bedtime (5 cycles, 7.5 h)22:45
- Minimum (4 cycles, 6 h)00:15
Frequently asked questions
Is every cycle exactly 90 minutes?
No — cycles range from 70 to 120 minutes and lengthen through the night, so treat these as close approximations.
Is 6 hours enough?
For most adults no. The evidence supports 7–9 hours; 6 is a fallback, not a target.
What do I need to enter into the Sleep Cycle Calculator?
Just 2 values: wake-up time (24h clock), minutes to fall asleep. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Sleep Cycle Calculator work out the answer?
Sleep runs in roughly 90-minute cycles, so waking at the end of a cycle — after 5 or 6 cycles — feels far better than waking mid-cycle. It applies the formula Sleep time = 90 min × cycles + 15 min to fall asleep and shows the working so you can check each step by hand.
Is the Sleep Cycle Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.