How long should a nap be?

3 min read

After lunch, I get unbearably sleepy. A short nap should clear my head, but I wake up feeling heavier instead.

It seems some naps help and some backfire. What separates them is length.

A 10-minute nap was the most effective

In an Australian experiment, 24 young adults whose sleep had been restricted to five hours the night before took afternoon naps of 0, 5, 10, 20, or 30 minutes, and their sleepiness and task performance afterward were compared [1].

Compared with no nap, a 10-minute nap reduced sleepiness and improved performance right from waking. The researchers concluded that among the lengths tested, 10 minutes was the most effective.

Sleep longer, and you wake up groggy

On the other hand, a 30-minute nap actually made sleepiness and performance worse right after waking [1]. If you wake just as you're entering deep sleep, your head stays foggy for a while. This is called "sleep inertia."

If you feel heavy after a nap, it may be because you slept too long and woke up in that state.

Have coffee before the nap

A Japanese experiment reported that taking caffeine just before a 20-minute nap led to less sleepiness and better performance after waking than either the nap alone or caffeine alone [2]. Caffeine takes time to kick in after you drink it, so the idea is that it starts working right around when you wake up.

But this was a small experiment with ten university students. And as I wrote in "Is coffee really bad for you?", there's an experiment where caffeine even six hours before bed shortened night sleep. If you try it, keep it to the early afternoon only.

How to nap

• Length: aim for 10–20 minutes, and set an alarm
• Time of day: early afternoon. Napping in the evening makes it harder to fall asleep at night
• Position: head down on a desk, leaning back in a chair, or some other position where you won't sleep too deeply
• Coffee: if you use it, have it right before the nap. Avoid it in the evening

A nap is not a substitute for night sleep

A nap temporarily eases afternoon sleepiness. As I wrote in "Can you catch up on lost sleep on the weekend?", the effects of sleep loss don't always go away even if you sleep more later.

If you're very sleepy almost every day, you may not be getting enough sleep at night, or a sleep disorder may be hidden. If it continues, talk to a doctor.