Bedtime & Wake-Up Calculator
Waking up in the middle of a deep sleep stage is what makes mornings brutal. Plan around full 90-minute sleep cycles instead, and wake up between them.
To wake up refreshed, go to bed at one of these times (each is a whole number of 90-minute sleep cycles, plus 15 minutes to fall asleep):
Last Alarm makes sure you are up when you planned to be.
How the sleep cycle calculator works
Your sleep is not one long block. It moves through cycles of roughly 90 minutes, from light sleep down to deep sleep and back up. Waking up near the top of a cycle feels natural. Waking up in the middle of deep sleep triggers grogginess, the heavy feeling known as sleep inertia.
This calculator counts backward or forward in whole 90-minute cycles and adds about 15 minutes for the time it takes to fall asleep. Aiming for five or six cycles gives you the 7.5 to 9 hours most adults need, ending on a natural wake point.
Of course, none of this helps if you sleep through the alarm. That is where Last Alarm comes in: it will not switch off until you complete a quick task, so the wake time you planned is the wake time you get.