Tool4SaaS

Sleep Calculator

Find best bedtime or wake time with 90-minute sleep cycles. Pick wake-up or bedtime, add fall-asleep time —, private, runs in browser.

We count 90-min cycles backwards

Avg. time to fall asleep

Go to bed at one of these times to wake at 7:00 AM
9:45 PM
6 cycles · 9h sleep
Recommended (5–6 cycles)
11:15 PM
5 cycles · 7h 30m sleep
Recommended (5–6 cycles)
12:45 AM
4 cycles · 6h sleep
4 cycles
2:15 AM
3 cycles · 4h 30m sleep
3 cycles
3:45 AM
2 cycles · 3h sleep
2 cycles
5:15 AM
1 cycles · 1h 30m sleep
1 cycles
Each cycle is 90 minutes. Includes 15 min to fall asleep. Adults usually feel best with 5–6 full cycles (7.5–9h).
How it works

Sleep runs in ~90-minute cycles. Waking at the end of a cycle feels more refreshing than waking mid-cycle. In “Wake up at” mode we subtract cycles backwards from your alarm; in “Sleep at” mode we add cycles forwards from your bedtime.

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About the author

Written and maintained by the Tool4SaaS team. Every tool runs locally in your browser and is tested in-house for accuracy. Last updated: .

Frequently asked questions

Average sleep cycle is 90 minutes; waking between cycles reduces grogginess.

No, for informational purposes only. Consult a healthcare professional for personal guidance.

Yes, it is free, works offline in your browser, and your data never leaves your device.

How to use Sleep Calculator

  1. Choose mode: Pick wake-up or bedtime mode.
  2. Enter time: Set target time.
  3. View: See 5-6 cycle options.