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Sleep calculator
Know when you need to be up, but not when to head to bed? Or already heading to bed and wondering where to put your alarm? Choose a direction below. This calculator shows four possible schedules, based on a simple 90-minute cycle and your estimated time to fall asleep.
Start with the highlighted five- and six-cycle options, then compare them with the time you actually have. Those highlights are planning suggestions within the model, not personal sleep recommendations. The time spent falling asleep is separate from the hours shown as sleep.
You have a wake-up time. Set it in Alarmeee and start with a photo task.
Pick one practical first step, such as making your bed. Enter the alarm time in the app and photograph the completed task there. Alarmeee checks the photo; this calculator simply helps you choose the time.
App StoreHow the times are worked out
For a fixed wake-up time, we count backwards by the number of cycles, then subtract your time to fall asleep. Each result shows when to get into bed and the estimated moment you fall asleep. For a bedtime, we add that delay first and then count forwards to possible wake-up times.
With a 7:00 AM alarm, five cycles mean 7 hours 30 minutes of modelled sleep. With a 15-minute delay, get into bed at 11:15 PM the previous day and allow until 11:30 PM to fall asleep. Six cycles move bedtime to 9:45 PM. Changing the delay changes bedtime, not the sleep duration.
Going to bed now uses the local clock on your device when you press Calculate. Choosing a specific bedtime lets you plan ahead. Results label the previous or next day whenever the calculation crosses midnight. They describe clock times rather than dated appointments; travel and daylight-saving changes need a separate check.
Bedtime = wake-up time − (cycles × 90 minutes) − time to fall asleep
Wake-up time = bedtime + time to fall asleep + (cycles × 90 minutes)
A useful estimate, with limits
Real sleep is not a timer that repeats precisely every 90 minutes. The NIH’s NHLBI describes cycles of 80–100 minutes. Our fixed value makes the arithmetic easy to compare, but cannot identify your sleep stages or guarantee waking between them.
The default 15 minutes is an editable guess, not a measurement of your night. Set it to a value that makes sense for planning. Brief awakenings and changes from one night to another are not included. Shorter options are shown for comparison, not as a reason to cut your sleep short.
Use the result alongside your own schedule and sleep needs. This is not medical advice, a diagnosis or a treatment. If sleep problems or persistent tiredness concern you, speak with a healthcare professional rather than trying to fix them by picking a different cycle count.
Questions and answers
Are sleep cycles always 90 minutes?
No. The calculator uses 90 minutes as a fixed planning assumption. Real cycles vary, so a calculated time cannot tell you which sleep stage you will be in when the alarm rings.
Why are five and six cycles highlighted?
They give 7 hours 30 minutes and 9 hours in this model. They are starting points for comparing schedules, not a prescription for your needs or a guarantee that either option will suit you.
Does the result include time to fall asleep?
The bedtime and wake-up calculations include your chosen delay. The sleep duration beside each result only counts the cycles. With five cycles and a 15-minute delay, the total time in bed is 7 hours 45 minutes.
What happens if a result crosses midnight?
The clock wraps to the appropriate time and the result says previous day or next day. Check the actual calendar date before setting an alarm, especially if you are planning a trip or a clock change.
Does this page set an alarm for me?
No. It calculates possible times. Choose a wake-up time and enter it in Alarmeee or another alarm yourself. The App Store button opens the app listing; it does not transfer your result or schedule a notification.
Do I need an account or share my sleep data?
No account is needed for this calculator. The time and delay you enter stay in this page while you use it, and the calculation runs on your device. Reloading the page starts again with the defaults.
You have a wake-up time. Set it in Alarmeee and start with a photo task.
Pick one practical first step, such as making your bed. Enter the alarm time in the app and photograph the completed task there. Alarmeee checks the photo; this calculator simply helps you choose the time.
App Store