About the Sleep Cycle Calculator
How many 90-minute sleep cycles fit into your sleep window, and the ideal duration for whole cycles.
Also known as: 90 minute sleep cycles, rem cycles, sleep cycle length.
How to use this calculator
- Enter hours of sleep, cycle length.
- The result updates instantly as you type — press Calculate (or Enter) at any time.
- Review the breakdown shown under the main result.
- Use Copy result or Share to save the answer or send a link with your inputs.
Formula
Cycles = sleep minutes ÷ cycle length
Worked example
Using the values pre-filled in the calculator above:
- Hours of sleep = 7.5
- Cycle length = 90 min
the calculator returns:
- Sleep cycles: 5
- Ideal sleep (whole cycles): 7.5 hours
- Minutes into current cycle: 0 min