Wake Up Time Calculator
Best bedtimes based on 90-minute sleep cycles.
Enter your values
Enter the wake hour (24h) you are working with.
Enter the wake minute you are working with.
Enter the time 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)
- 21:45
- 5 cycles (7.5 h)
- 23:15
- 4 cycles (6 h)
- 00:45
- Fall-asleep allowance
- 15 min
Quick answer
Waking at the end of a 90-minute cycle feels easier than waking mid-cycle, so bedtimes should be set in 90-minute steps.
bedtime = wake time - (cycles x 90 min) - fall-asleep time
At a glance
| What it does | Best bedtimes based on 90-minute sleep cycles. |
|---|---|
| Category | Health |
| Inputs needed | Wake hour (24h), Wake minute, Time to fall asleep |
| Main output | Best bedtime (6 cycles) |
| Formula | bedtime = wake time - (cycles x 90 min) - fall-asleep time |
| Cost | Free — no sign-up, no download |
How to use the Wake Up Time Calculator
- 1Enter the time your alarm goes off.
- 2Allow 10-20 minutes to actually fall asleep.
- 3Pick the bedtime that gives you five or six full cycles.
Inputs explained
- Wake hour (24h)
- Enter the wake hour (24h) you are working with.
- Wake minute
- Enter the wake minute you are working with.
- Time to fall asleep(min)
- Enter the time to fall asleep in min.
Worked example
Using the values the calculator loads with:
Inputs
- Wake hour (24h)7
- Wake minute0
- Time to fall asleep15 min
Results
- Best bedtime (6 cycles)21:45
- 5 cycles (7.5 h)23:15
- 4 cycles (6 h)00:45
- Fall-asleep allowance15 min
Frequently asked questions
Are cycles always 90 minutes?
They range from 80 to 110 minutes and change through the night; treat this as a guide.
Is six cycles always best?
Nine hours suits some people; most adults do well on five or six cycles.
What do I need to enter into the Wake Up Time Calculator?
Just 3 values: wake hour (24h), wake minute, time 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 Wake Up Time Calculator work out the answer?
Waking at the end of a 90-minute cycle feels easier than waking mid-cycle, so bedtimes should be set in 90-minute steps. It applies the formula bedtime = wake time - (cycles x 90 min) - fall-asleep time and shows the working so you can check each step by hand.
Is the Wake Up Time 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.