Calculator
Nap Calculator: Estimate an Alarm Time
Choose a nap start time and duration to estimate when to set your alarm, including optional time to fall asleep.
Free sleep planning tool
Nap Calculator
Choose a nap start time and duration to estimate an alarm time.
Your estimates
Suggested times
Show shorter estimates
Actual sleep cycles and time to fall asleep vary. Adequate total sleep and how rested you feel matter more than matching an exact cycle.
Method
What the calculator is estimating
Cycle duration
The default is 90 minutes, but the calculator allows 80 to 110 minutes because real sleep cycles are not identical.
Time to fall asleep
The default adds 15 minutes before estimated sleep begins. You can change it to match your own planning assumption.
Total sleep time
Every result displays estimated time asleep. Cycle timing should never be used to justify routinely cutting sleep short.
Why the times are estimates
Sleep is organized into non-REM and REM phases. The National Heart, Lung, and Blood Institute explains that a cycle commonly restarts every 80 to 100 minutes and that people usually complete four to six cycles per night. The exact pattern changes through the night and across a lifetime.
A clock-based calculator cannot know when you actually fall asleep or identify your sleep stages. It can only create a schedule from the assumptions you choose. Use the results as a convenient planning reference and pay attention to whether you obtain enough sleep and feel rested.
How much sleep should you allow?
Sleep needs change with age. Current CDC guidance says adults ages 18 to 60 should generally get at least seven hours daily, while teenagers commonly need eight to ten hours. Children and younger age groups generally need more. Visit Sleep by Age before applying an adult-oriented schedule to a child or teenager.