How long should a nap be? The 10, 20 and 90 minute rule

A good nap can sharpen your attention and lift your mood for hours. A badly timed one leaves you groggy and wrecks that night’s sleep. The difference is mostly length and timing.

Short naps: 10 to 20 minutes

For a quick boost, short is best. In a study comparing nap lengths after a short night, a 10-minute nap gave the fastest, longest-lasting improvement in alertness and performance, with almost no grogginess afterwards. Naps of around 20 minutes also helped, though the benefit took a little longer to arrive.

The reason is sleep stages. In the first 15 to 20 minutes you’re in light sleep. Wake then and you surface easily. Sleep longer and you start sliding into deep sleep, and waking from deep sleep causes sleep inertia: that heavy, confused feeling that can last half an hour.

The awkward middle: 30 to 60 minutes

Naps in this range often end right in deep sleep. You may wake up feeling worse than before, at least for a while. If you only have 45 minutes, set an alarm for 20.

Full-cycle naps: about 90 minutes

A nap of around 90 minutes lets you go through a complete sleep cycle, including deep sleep and REM, and wake near the end of it. These can help after a seriously short night or before a long night shift. The trade-off: they can make it harder to fall asleep that night, so they’re not for every day. The sleep calculator’s cycle logic applies to naps too.

When to nap

Most people have a natural dip in alertness in the early afternoon, roughly 1 to 3 PM. That’s the best window. Napping later in the afternoon or evening eats into the sleep pressure you need to fall asleep at bedtime.

Tips for a better nap

1. Set an alarm for the length you want, plus a few minutes to fall asleep.
2. Lie down somewhere dark and quiet, or use an eye mask.
3. Try a “coffee nap” if you’re not sensitive to caffeine: drink a coffee right before a 20-minute nap. Caffeine takes about that long to kick in. Skip this one in the afternoon if it affects your sleep.
4. Don’t nap to replace night sleep. If you need a nap every day, look at your nighttime sleep first.

Frequent, overwhelming daytime sleepiness despite enough sleep at night is worth discussing with a doctor. It can be a sign of sleep apnea or another sleep disorder.

Sources

• Brooks A, Lack L. A brief afternoon nap following nocturnal sleep restriction: which nap duration is most recuperative? Sleep. 2006;29(6):831-840.
• Milner CE, Cote KA. Benefits of napping in healthy adults: impact of nap length, time of day, age, and experience with napping. Journal of Sleep Research. 2009;18(2):272-281.
• Hayashi M, Masuda A, Hori T. The alerting effects of caffeine, bright light and face washing after a short daytime nap. Clinical Neurophysiology. 2003;114(12):2268-2278.