Caffeine vs WaterEnergy
The Coffee Nap: Does It Work, and How to Do It Right
A coffee nap is coffee drunk right before a 20-minute nap. Studies show it beats either alone. How to time it, what to drink and when it backfires.
The short answer
- A coffee nap is a caffeinated drink finished quickly, followed straight away by a nap of 15–20 minutes. You wake up just as the caffeine starts to work.
- Does a coffee nap work? In small lab studies, yes: in a driving simulator, caffeine plus a short nap cut driving incidents to 9% of placebo levels, against 34% for caffeine alone.
- Use about 100–200 mg of caffeine you can finish in a few minutes, such as a double espresso (126 mg) or a 10 oz cold brew (155 mg).
- Keep it early. A 126 mg coffee nap at 2 pm leaves about 42 mg at an 11 pm bedtime; at 4 pm it's about 54 mg.
Drinking coffee right before a nap sounds like a contradiction. But the coffee nap has some of the better evidence of any "energy hack": it was first tested on sleepy drivers in a British sleep lab in the 1990s, and it has held up in studies on afternoon slumps and night-shift work since. The trick is all in the timing. Here's what the research found, how to do one properly, and when it will cost you sleep later.
How a coffee nap works
Two things happen at once, and they happen to line up.
Caffeine takes a while to arrive. After you drink it, caffeine is absorbed from your gut into your blood over the next half-hour or so. In one classic study, blood levels peaked about 30 minutes after an oral dose. In the model our app uses, a drink reaches about 80% of its peak effect roughly 20 minutes in. So for the first 15–20 minutes, you're not getting much of the alerting effect yet.
A short nap clears sleepiness without deep sleep. A nap of 15–20 minutes mostly stays in light sleep. You wake up easily, without the grogginess (called sleep inertia) you get after waking from deep sleep in a longer nap.
Put the two together and you use the caffeine's lag time for something useful. You fall asleep before the caffeine kicks in, and wake up just as it does. A popular explanation adds that the nap clears some adenosine, the chemical behind sleep pressure, so the caffeine has fewer receptors to fight for. That's plausible, but it hasn't been directly measured in the coffee nap studies, so treat it as a theory. The practical results are what's been tested.
Does a coffee nap work? What the studies show
Sleepy drivers, 1996. Researchers at Loughborough University had sleepy volunteers drive a car simulator, with a 30-minute break in between. During the break they had either a nap of under 15 minutes, 150 mg of caffeine in coffee, or a decaf placebo. Both the nap and the caffeine cut driving errors and sleepiness. Just taking a break did nothing.
The combination, 1997. The same team then combined them: 200 mg of caffeine followed by a short nap, before a 2-hour afternoon drive. Compared with placebo, caffeine alone cut driving incidents to 34%. Caffeine plus the nap cut them to 9%, and removed the usual mid-afternoon peak in sleepiness altogether. Even people who only dozed without properly falling asleep still got the benefit.
The afternoon slump, 2003. A Japanese study compared a 20-minute nap on its own with a nap plus 200 mg of caffeine beforehand, a nap plus bright light, and a nap plus face washing. The coffee nap was the most effective for both sleepiness and performance, and the effect lasted the full hour afterwards.
Night shifts, 2006. In lab and field studies of night-shift workers, a nap and caffeine each improved alertness, but the combination worked best. More on that in caffeine for shift work.
How to take a coffee nap
- Pick the right time. Early afternoon is ideal, when the natural post-lunch dip hits. Aim to finish by about 2–3 pm if you sleep at 11 pm.
- Drink fast. Choose something you can finish in a few minutes: an espresso, a cold brew or an iced coffee. A scalding 16 oz latte sipped over 20 minutes defeats the point.
- Lie down straight away. Set a timer for 20 minutes. Don't worry if you don't fully fall asleep; dozing still counted in the studies.
- Don't go longer than 20–25 minutes. Longer naps drift into deep sleep, and waking from that makes you groggier, not sharper.
- Get up and get light. Open the blinds or step outside. Bright light after a nap helped almost as much as caffeine in the 2003 study.
What to drink for a coffee nap
The studies used 150–200 mg. Most people get a good effect from 100–150 mg. Here's how common options compare, including how much would still be in your system at an 11 pm bedtime for a typical metaboliser:
| Drink | Caffeine | Left at 11 pm if at 1 pm | If at 2 pm | If at 4 pm |
|---|---|---|---|---|
| Single espresso, 1 oz (30 ml) | 63 mg | 18 mg | 21 mg | 27 mg |
| Red Bull, 8.4 oz (250 ml) | 80 mg | 23 mg | 27 mg | 34 mg |
| Iced coffee, 12 oz (350 ml) | 120 mg | 35 mg | 40 mg | 51 mg |
| Double espresso, 2 oz (60 ml) | 126 mg | 37 mg | 42 mg | 54 mg |
| Cold brew, 10 oz (300 ml) | 155 mg | 45 mg | 51 mg | 66 mg |
| Celsius, 12 oz (355 ml), or a 200 mg caffeine pill | 200 mg | 58 mg | 66 mg | 85 mg |
A double espresso is the sweet spot for most people: enough caffeine to feel, quick to drink, and under the 50 mg sleep line by bedtime if you have it by about 2 pm. A 200 mg dose, like the one used in the studies, is better saved for mornings or for night shifts. For a full list of drinks, see the caffeine content chart, or check a drink and time against your bedtime with the caffeine calculator.
When a coffee nap backfires
- Too late in the day. A 4 pm coffee nap with a cold brew leaves about 66 mg at 11 pm, enough to affect deep sleep. That sets up a worse night and a bigger slump tomorrow. See is 2 pm too late for coffee? for the numbers by drink.
- Too long a nap. Past about 25–30 minutes you're more likely to wake from deep sleep, feel foggy, and have trouble falling asleep at night.
- Too much caffeine. If you're sensitive or anxious, 200 mg on top of your morning coffee can bring on jitters or a racing heart. Stick to 60–100 mg, or skip the coffee and just nap. Our guide on caffeine and anxiety has more.
- As a daily fix for too little sleep. If you need a coffee nap every day to function, the real problem is the night before. A common cause is caffeine late in the day reducing deep sleep, so you wake up unrefreshed; see caffeine and deep sleep.
If you're pregnant, have a heart condition, or take medication that interacts with caffeine, check with your doctor before using caffeine to fight sleepiness.
Frequently asked questions
Does a coffee nap work?
In small controlled studies, yes. Caffeine followed by a short nap reduced sleepiness and improved performance more than either caffeine or a nap alone. In one driving simulator study, the combination cut driving incidents to 9% of placebo levels, compared with 34% for caffeine alone.
How long should a coffee nap be?
About 15–20 minutes. That's long enough to rest but short enough to avoid deep sleep, and it matches the time it takes caffeine to start working.
How much caffeine should I have before a coffee nap?
Studies used 150–200 mg. For most people, 100–150 mg, such as a double espresso (126 mg), works well and is less likely to affect sleep that night.
What if I can't fall asleep during a coffee nap?
That's fine. In the 1997 driving study, even "nonsleep dozing" was effective. Lying down quietly with your eyes closed for 15–20 minutes still helps.
What is the best time for a coffee nap?
Early afternoon, around 1–2 pm, when most people have a natural dip in alertness. Later than about 3 pm, the caffeine is more likely to still be in your system at bedtime.
Sources
- Horne JA, Reyner LA. Counteracting driver sleepiness: effects of napping, caffeine, and placebo. Psychophysiology, 1996.
- Reyner LA, Horne JA. Suppression of sleepiness in drivers: combination of caffeine with a short nap. Psychophysiology, 1997.
- Hayashi M, et al. The alerting effects of caffeine, bright light and face washing after a short daytime nap. Clin Neurophysiol, 2003.
- Schweitzer PK, et al. Laboratory and field studies of naps and caffeine as practical countermeasures for sleep-wake problems associated with night work. Sleep, 2006.
- Blanchard J, Sawers SJ. The absolute bioavailability of caffeine in man. Eur J Clin Pharmacol, 1983.
General wellness information, not medical advice. If you're pregnant, have a heart condition, or take medication that affects caffeine, check your limits with a doctor.