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About this tool
Pick a nap length and alarm time that avoids sleep inertia, fits before your next commitment and protects tonight's sleep.
The Power Nap Planner works out which nap length fits the time you have and what to set the alarm for, so you wake before slow-wave sleep rather than in the middle of it. Slow-wave sleep typically begins about 20 minutes into a nap, which is why a 10-20 minute nap leaves you clear-headed while a 30-45 minute one leaves you groggier than before — the effect known as sleep inertia. It also checks the nap against tonight's bedtime, since napping within six hours of bed bleeds off the sleep pressure you need to fall asleep.
Open Power Nap Planner on AltFTool — it loads instantly in your browser.
Add your input to the workspace.
Adjust the options until the result looks right.
Copy or download the output and put it to work.
Ranks each option by the grogginess it causes, not just its length, and marks the 30-minute nap as the worst choice.
Adds your own sleep latency and the recovery time after waking, then rules out anything that will not fit.
Flags naps that end within six hours of bedtime instead of treating daytime alertness as the only goal.
Ten to twenty minutes of actual sleep. That keeps you in light N1 and N2 sleep and restores alertness without sleep inertia. Add your own falling-asleep time on top — most adults take 10-15 minutes, so a 20-minute nap usually means setting an alarm for about 35 minutes after you lie down.
Because 30 minutes lands you in early slow-wave sleep, the deepest stage, and waking from it triggers sleep inertia — the heavy, disoriented feeling that can last 15 to 30 minutes. Either finish before slow-wave sleep starts at around 20 minutes, or sleep a full cycle of about 90 minutes so you surface through lighter sleep again.
You drink a coffee immediately before a nap of 20 minutes or less. Caffeine takes about 20-30 minutes to reach peak concentration in the blood, so it arrives just as you wake, and it clears adenosine receptors that the nap has already partly emptied. Studies of driver alertness have found the combination beats either a nap or coffee alone.
Finish at least six hours before your intended bedtime, and ideally nap in the post-lunch circadian dip between about 13:00 and 15:00. Napping later still relieves sleepiness but spends the sleep pressure you need at night, which is why evening naps so often turn into a 2 a.m. stare at the ceiling. If you need daily naps despite sleeping normally at night, mention it to a doctor.