Sleep Calculator

How this is calculated

Sleep happens in cycles of roughly 90 minutes, and waking up in the middle of a cycle is what tends to make people feel groggy — waking up at the boundary between cycles tends to feel better, even with less total sleep. This calculator counts back from your wake-up time in 90-minute blocks, and adds 15 minutes on top as a typical amount of time it takes to actually fall asleep after getting into bed.

These are estimates based on average cycle length, not a measurement of your actual sleep — individual cycles vary somewhat from person to person and night to night. Use it as a starting point, not a guarantee.