Sleep Calculator
Plan when to go to bed or when to wake up using full 90-minute sleep cycles. It is a simple way to avoid waking up in the middle of deep sleep and feel more rested.
We include about 15 minutes to fall asleep, then line up full 90-minute sleep cycles.
More recovery
9:45 PM
6 cycles
About 9 hours
Most balanced
11:15 PM
5 cycles
About 7.5 hours
Shorter night
12:45 AM
4 cycles
About 6 hours
Light → deep
Repair + memory
Repair + memory
Repair + memory
REM-heavy
Most people feel better waking up between cycles instead of during deep sleep. Five cycles, about 7.5 hours asleep, is a practical target for many adults.
Recommended sleep by age
Teenagers (13-18)
8-10 hours
Adults (18-64)
7-9 hours
Older adults (65+)
7-8 hours
These ranges are based on general sleep foundation guidance. Your ideal amount can vary with training load, stress, illness, and sleep quality.
How to Use
- Choose Bedtime Calculator if you know when you need to wake up, or Wake Time Calculator if you know when you are going to bed.
- Enter your wake-up time or bedtime using the time field.
- Review the suggested times based on 4, 5, and 6 complete sleep cycles, with 15 minutes included for falling asleep.
- Compare the results with the recommended sleep duration by age to choose the option that fits your schedule and recovery needs.
Frequently Asked Questions
How long is one sleep cycle?
A full sleep cycle is commonly estimated at about 90 minutes, though it can vary from person to person. This calculator uses 90 minutes as a practical average for planning bedtimes and wake-up times.
Why does the calculator add 15 minutes?
Most people do not fall asleep instantly. Adding about 15 minutes makes the suggested times more realistic by accounting for the time it takes to settle in and actually fall asleep.
Is 6 hours of sleep enough?
For most adults, 6 hours is below the generally recommended 7 to 9 hours per night. It may be workable occasionally, but 5 or 6 full cycles usually feel better than only 4 over the long term.
Does waking between cycles really help?
It often does. Waking during lighter sleep can reduce grogginess compared with waking from deep sleep. Sleep quality, consistency, and total duration still matter just as much.