Plan nap length and timing.
Nap length decides how you feel on waking. Twenty minutes stays in light sleep and avoids grogginess; ninety minutes completes a cycle and also wakes you cleanly; the middle ground risks being woken out of deep sleep. The alarm time adds the minutes you take to fall asleep, and the gap before bedtime matters because napping too late erodes the sleep pressure you need at night.
Nap timing
Alarm time = nap start + minutes to fall asleep + nap length (20 power / 60 recovery / 90 full cycle); gap = bedtime - alarm time
These figures are estimates based on population-average formulas and are intended for training and recreational planning only. They are not medical advice. Consult a qualified health professional before starting or changing an exercise programme, particularly if you have an existing medical condition.
Twenty minutes for alertness without grogginess, or ninety for a full cycle if you have the time. Forty to sixty minutes often produces the worst wake-up because it interrupts deep sleep.
Aim to be awake at least six hours before bedtime. Later naps reduce the sleep pressure that helps you fall asleep at night.
Sleep inertia. Waking from deep sleep leaves you groggy for ten to thirty minutes, which is why short naps or full cycles are preferred.