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Sleep Cycle Calculator
Count back in 90-minute sleep cycles from your wake-up time to find the best times to go to bed.
Favorite it to find it fast on home
When to use it
Wake at 7:00 → bed at 22:15 for five cycles
Wake at 6:00 → choose 21:45 or 23:15
Falling asleep in 15 minutes shifts the plan earlier
How to use it
1Step 1Fill in Wake-up time
2Step 2Change a value and the result updates instantly
3Step 3Save or copy the result
If the result looks off
The result looks wrong
Check the units and the baseline first. Changing a value updates the result instantly.
I want the starting values back
Press reset to return to the initial state.
Frequently asked questions
Why 90 minutes?
One REM-plus-non-REM cycle is about 90 minutes, so waking at a cycle boundary feels easier.
Does falling asleep time matter?
Yes — the minutes you need to drift off are subtracted before counting cycles.
How many cycles do I need?
Most adults do best with five or six cycles, so four is the minimum shown.