Power Nap vs Full Cycle Calculator

About this calculator

Sleep progresses in cycles of roughly 90 minutes, moving from light sleep down through deep slow-wave sleep and up into REM before starting over. A power nap of about 20 minutes is timed to end while you are still in light sleep, so you wake up quickly and clear-headed; a full 90-minute nap instead lets you complete an entire cycle, including REM, and wake up at a naturally lighter point rather than being pulled out of deep sleep.

Waking up in the middle of deep sleep — which happens if a nap runs somewhere between about 30 and 60 minutes — tends to cause sleep inertia: the groggy, disoriented feeling that can outlast the nap's supposed benefit. Shift workers, students cramming between classes, and anyone fitting a rest break into a busy afternoon use this distinction to choose a nap length that matches the time they actually have rather than waking up worse off than before they lay down.

Enter how much time you have available and the calculator tells you whether a short power nap or a full sleep cycle fits, so you avoid waking up in the groggy zone in between.