Sleep Calculator
Optimize your sleep schedule for better rest and productivity
Calculate optimal bedtimes based on your natural sleep cycles to wake up feeling refreshed.
Calculate when to go to bed or wake up based on your desired sleep duration.
Sleep Calculator
Stop waking up groggy! If you rely on an alarm only to feel foggy, tired, and irritable, the problem likely isn’t how long you sleep—it’s when you wake up. Our Sleep Calculator is the science-backed tool you need to optimize your rest and conquer sleep inertia every morning.
The key to feeling refreshed is aligning your wake-up time with the end of a complete sleep cycle. The average human sleep cycle lasts approximately 90 minutes. Waking during the lighter stages of sleep, rather than deep sleep, makes all the difference.
The Power of Timing: Sleep Cycle Calculation
This primary function of our Sleep Calculator helps you reverse-engineer the perfect bedtime based on your biological rhythm.
How the Sleep Cycle Calculator Works:
You simply input the time you need to wake up, and the tool instantly calculates optimal bedtimes by adding or subtracting full 90-minute cycles:
Set Your Target: Choose whether you want to calculate the bedtime from a fixed wake-up time, or calculate the wake-up time from a fixed bedtime.
Adjust Settings (Optional): While the tool defaults to the widely accepted 90-minute sleep cycle length, you can adjust this setting, along with the estimated time to fall asleep (defaulting to 15 minutes).
Calculate: Hit “Calculate Sleep Times.”
The results prominently feature 5 and 6 full cycles—the most recommended targets for adults.
Pro Tip: Waking after 5 cycles (approx. 7.5 hours total) or 6 cycles (approx. 9 hours total) provides the best chance of avoiding sleep inertia and feeling sharp upon waking.
Sleep Duration Calculation: Hitting Your Sleep Goal
While cycle timing is vital, total sleep quantity matters too. Our Sleep Calculator also features a straightforward Sleep Length Calculator to ensure you meet your daily requirement.
If you know you need 7 hours and 30 minutes of sleep to feel your best, use this feature to pinpoint the exact time you need to be asleep, given your set alarm. Conversely, input your bedtime to see how long you will sleep.
When to Use the Duration Tool:
When your schedule demands a fixed, exact duration (e.g., for athletes or shift workers).
When confirming if your current habits meet the recommended 7–9 hours for adults.
Related Calculators:
For most adults, aiming for 5 full sleep cycles (7.5 hours) or 6 full sleep cycles (9 hours) is ideal. This range ensures you complete several cycles of deep and REM sleep before waking. Our calculator prioritizes these options.
The average sleep cycle time is between 90 and 110 minutes. We use 90 minutes in the primary calculation as it is the most commonly cited and effective timeframe for optimizing alarms.
Sleep inertia is the temporary cognitive impairment and grogginess experienced immediately after waking. It is significantly minimized when you wake up naturally at the end of a sleep cycle, which is what our Sleep Calculator helps you achieve.
Yes! While children may have slightly different cycle lengths, this bedtime calculator is a fantastic starting point. You can use the settings to adjust the cycle length based on pediatric sleep recommendations for tailored results.