😴 Sleep Calculator
Enter your bedtime and wake-up time to see your total sleep duration and how many complete 90-minute sleep cycles you’ll get.
Why sleep cycles matter
Sleep happens in cycles of roughly 90 minutes that move through lighter and deeper stages, including REM sleep. Many people report feeling more refreshed when they wake up at the end of a complete cycle rather than in the middle of a deep-sleep stage, which is why some sleep guidance is built around multiples of 90 minutes rather than a flat number of hours.
How this calculator works
Enter the hour and minute you plan to go to bed and the hour and minute you plan to wake up, both on a 24-hour clock (for example, 11:00 PM is hour 23, minute 0). The calculator finds the total time between those two points, then divides it by 90 minutes to show how many complete sleep cycles fit in that window, along with how many extra minutes fall outside a full cycle.
Individual sleep needs and cycle lengths vary from person to person, and this calculator provides a general estimate rather than a personalized recommendation. It is intended for general planning and educational purposes only and does not replace guidance from a healthcare provider for ongoing sleep problems.