Energy drinks hurt sleep mainly because of how much caffeine they pack: a 16 oz can often holds about 160 mg, and at an average 5-hour half-life that takes more than 13 hours to fall below 25 mg. For a 10:30 PM bedtime, that means finishing a big can by about 9 AM. A small 8.4 oz can gives you until early afternoon.
Free toolCaffeine Cutoff CalculatorHow much caffeine is still in you at bedtime, and your latest cup.How much caffeine is in an energy drink?
Energy drinks range from about 40 to 250 mg of caffeine per 8 oz, a much wider spread than coffee. The FDA says most 16 oz energy drinks carry 54 to 328 mg. Can sizes vary too, so the number on the front matters less than the total on the label.
- Small cans (about 8 oz): often around 80 mg, similar to a cup of coffee.
- Standard 16 oz cans: often around 160 mg, close to two coffees.
- High-caffeine cans: 200 to 300 mg or more in a single can.
A few things make the true total easy to miss. Guarana is itself a source of caffeine. Sugar-free doesn't mean caffeine-free. And drinking a can quickly, cold, while you're busy doesn't feel like "two coffees," even when it is.
Latest time to drink it, by can
Using the site's caffeine math (average 5-hour half-life, under 25 mg by bedtime):
| Caffeine in the can | Time to drop below 25 mg | Latest for 10:30 PM bed | Latest for 11:30 PM bed |
|---|---|---|---|
| 80 mg | 8 h 23 min | 2:05 PM | 3:05 PM |
| 160 mg | 13 h 23 min | 9:05 AM | 10:05 AM |
| 200 mg | 15 h 0 min | 7:30 AM | 8:30 AM |
| 300 mg | 17 h 55 min | 4:35 AM | 5:35 AM |
The last two rows are the uncomfortable part. A 200 mg can at breakfast is already at the limit, and a 300 mg can can't clear to 25 mg by a normal bedtime no matter when you wake up. That doesn't mean one can at 8 AM will ruin your night, but it does mean the leftover caffeine is still working on your sleep.
The caffeine calculator works out your exact cutoff for any can size, bedtime and sensitivity.
What research shows about energy drinks and sleep
A 2024 national survey of more than 53,000 Norwegian college and university students found that the more often people drank energy drinks, the shorter and less efficient their sleep tended to be, and the longer it took them to fall asleep. Daily drinkers were roughly twice as likely to report short sleep as students who rarely or never drank them. Even occasional use was linked to worse sleep.
That was a survey, so it shows an association rather than proof of cause. Some people may reach for energy drinks because they already sleep badly. But the pattern fits what lab studies show about caffeine: in one, a 400 mg dose taken 6 hours before bed cut total sleep by more than an hour.
The energy drink cycle
This is the trap many people fall into:
- Sleep badly.
- Drink a can to get through the afternoon.
- Sleep badly again because of the afternoon can.
- Need another can tomorrow.
Breaking it usually means accepting one or two rough afternoons while your sleep catches up. The sleep debt calculator can show you how far behind you are, which often explains why the afternoon slump feels so bad.
How to keep energy drinks from wrecking your sleep
- Make them a morning drink. Anything over 100 mg belongs before mid-morning if you care about sleep.
- Downsize. Switching from a 16 oz can to a small can roughly halves the caffeine.
- Count everything. Coffee, pre-workout and soda all add to the same total. The FDA suggests up to 400 mg a day is generally safe for healthy adults.
- Swap the afternoon can for water, a walk outside, or a 20-minute nap. The nap calculator helps you time it.
- Watch for side effects. Jitters, a racing heart or anxiety are signs you've had too much. Seek medical help if symptoms are severe.
If you use energy drinks for training, see pre-workout before bed, which covers evening workouts. For coffee and tea comparisons, see the caffeine in drinks chart.