Sleep Calculator
Calculate the best bedtime or wake-up time based on 90-minute sleep cycles. Waking up between cycles feels more refreshing than being jolted awake mid-cycle.
Go to bed at one of these times:
4 cycles
6.0 hrs
5 cycles
7.5 hrs
6 cycles
9.0 hrs
7 cycles
10.5 hrs
Other sleep calculators:
How it works
This sleep calculator runs entirely in your browser — no data is sent to any server. Simply fill in the fields above and the result updates instantly. You can copy the output with the copy button provided.
Frequently Asked Questions
How does the sleep cycle calculator work?
Sleep occurs in 90-minute cycles. Waking up at the end of a cycle (rather than mid-cycle) makes you feel more rested. The calculator adds 14 minutes for average sleep onset.
How many sleep cycles should I get?
Most adults feel best with 5–6 full sleep cycles (7.5–9 hours). Teenagers need more — typically 6–8 cycles.
What time should I go to bed to wake up at 6am?
To wake at 6:00am feeling refreshed, go to sleep at 8:46pm, 10:16pm, 11:46pm, or 1:16am — each being a full number of 90-minute cycles before your wake time.