sleep calculator

Wake up rested.

Sleep cycles are about 90 minutes long. Waking up between cycles feels much better than waking up in the middle of one.

to wake at 11:00 PM, fall asleep by:
6 cycles (9 h)OPTIMAL1:46 PM
5 cycles (7.5 h)OPTIMAL3:16 PM
4 cycles (6 h)4:46 PM
3 cycles (4.5 h)6:16 PM
How sleep cycles work. A full cycle is roughly 90 minutes and contains light sleep, deep sleep, and REM. Most adults need 5 to 6 cycles per night (7.5 to 9 hours). Allow about 14 minutes to actually fall asleep after lying down.

Frequently asked

Is this tool free?
Yes. The sleep calculator is completely free. Plan your bedtime or wake time as often as you like.
Do I need to sign up?
No. Pick a wake time or bedtime and see the results. No account required.
Is my data private?
All calculations run in your browser. No sleep data or times are sent to any server.
How does it calculate the best times?
It works in 90-minute sleep cycles (the average length of one full cycle) and adds 14 minutes for the time it takes to fall asleep. The results for 3 to 6 cycles are shown, with the optimal range of 7.5 to 9 hours highlighted.