Monster has more caffeine per can: a 16 oz Monster has 160 mg, while the classic 8.4 oz Red Bull has 80 mg, according to each brand's own figures. Can for can at the same 16 oz size, it's close: Monster 160 mg, Red Bull 151 mg. Per ounce they're almost the same, about 10 mg per fluid ounce for Monster and about 9.5 for Red Bull.
So the real difference is can size, not strength. A typical Monster is a 16 oz can, and a typical Red Bull is the small 8.4 oz one, which is why "a Monster" usually means about twice the caffeine of "a Red Bull." To see what either can leaves in you at bedtime, the caffeine calculator runs the numbers for your own times.
Free toolCaffeine Cutoff CalculatorHow much caffeine is still in you at bedtime, and your latest cup.What has more caffeine, Monster or Red Bull?
A standard 16 oz Monster (160 mg) has twice the caffeine of a standard 8.4 oz Red Bull (80 mg). Compare equal sizes and Monster is only slightly ahead. All figures below come from the brands' own US pages, the same ones used in our posts on Monster caffeine and Red Bull caffeine.
| Drink | Can size | Caffeine | Per fl oz |
|---|---|---|---|
| Red Bull (or Sugarfree) | 8.4 fl oz | 80 mg | about 9.5 mg |
| Red Bull | 12 fl oz | 114 mg | about 9.5 mg |
| Red Bull | 16 fl oz | 151 mg | about 9.4 mg |
| Red Bull | 20 fl oz | 198 mg | about 9.9 mg |
| Monster Energy (original green) | 16 fl oz | 160 mg | 10 mg |
| Monster Zero Ultra | 16 fl oz | 150 mg | about 9.4 mg |
| Rehab Monster | 15.5 fl oz | 160 mg | about 10.3 mg |
| Java Monster | 15 fl oz | 200 mg | about 13.3 mg |
Two things stand out. First, a 16 oz Red Bull and a 16 oz Monster are within 10 mg of each other. Second, Java Monster is the strongest drink in either lineup per ounce, because it's a coffee drink.
Recipes can change, and some flavors differ, so the can in your hand is the final word.
How much caffeine is in a Monster vs a Red Bull, ounce for ounce?
Ounce for ounce, Monster original has 10 mg per fl oz and Red Bull has about 9.5 mg, so they're nearly identical. The gap is small enough that you won't notice it. What you will notice is drinking 16 ounces instead of 8.4.
Red Bull's caffeine stays roughly in step with can size: the 20 oz can is almost exactly 2.5 small cans. Monster's main lines sit at about 9.4 to 10.3 mg per ounce, except Java Monster at about 13.3.
Monster compared to Red Bull vs a cup of coffee
An 8 oz cup of brewed coffee has about 95 mg of caffeine, so a small Red Bull is a bit less than one cup and a 16 oz Monster is about 1.7 cups. Here's each can expressed in cups of coffee:
| Drink | Caffeine | About this many 8 oz coffees |
|---|---|---|
| Red Bull, 8.4 oz | 80 mg | 0.8 |
| Red Bull, 12 oz | 114 mg | 1.2 |
| Red Bull, 16 oz | 151 mg | 1.6 |
| Monster original, 16 oz | 160 mg | 1.7 |
| Red Bull, 20 oz | 198 mg | 2.1 |
| Java Monster, 15 oz | 200 mg | 2.1 |
Coffee itself varies a lot with brew strength and cup size. A large coffee-shop drip can easily beat any of these cans. For more drinks side by side, see the caffeine in drinks chart.
Which one keeps you up later: Monster or Red Bull?
A 16 oz Monster at 2 PM leaves about 46 mg in you at 11 PM, while a small Red Bull at the same time leaves about 23 mg. The table uses the calculator's math: remaining caffeine = dose x 0.5^(hours / 5), with an average 5-hour half-life and an 11 PM bedtime.
| Can at | Red Bull 8.4 oz (80 mg) | Red Bull 16 oz (151 mg) | Monster 16 oz (160 mg) | Java Monster (200 mg) |
|---|---|---|---|---|
| 8 AM | 10 mg | 19 mg | 20 mg | 25 mg |
| 10 AM | 13 mg | 25 mg | 26 mg | 33 mg |
| Noon | 17 mg | 33 mg | 35 mg | 44 mg |
| 2 PM | 23 mg | 43 mg | 46 mg | 57 mg |
| 4 PM | 30 mg | 57 mg | 61 mg | 76 mg |
| 6 PM | 40 mg | 76 mg | 80 mg | 100 mg |
This site uses about 25 mg at bedtime as a sensible ceiling. It isn't an official limit, but it's a useful line. At equal 16 oz sizes the two brands land within a few milligrams of each other at bedtime, so the choice that matters for sleep is the size of the can and the time you drink it.
What's the latest time to drink a Monster or a Red Bull?
For an 11 PM bedtime, finish a small 8.4 oz Red Bull by about 2:37 PM, a 16 oz Red Bull by about 10:02 AM and a 16 oz Monster by about 9:37 AM. These are the times each can drops below 25 mg by bed:
| Bedtime | Red Bull 8.4 oz | Red Bull 16 oz | Monster 16 oz | Java Monster |
|---|---|---|---|---|
| 10:00 PM | 1:37 PM | 9:02 AM | 8:37 AM | 7:00 AM |
| 10:30 PM | 2:07 PM | 9:32 AM | 9:07 AM | 7:30 AM |
| 11:00 PM | 2:37 PM | 10:02 AM | 9:37 AM | 8:00 AM |
| Midnight | 3:37 PM | 11:02 AM | 10:37 AM | 9:00 AM |
In hours before bed, that's about 8 h 23 min for a small Red Bull, 12 h 58 min for a 16 oz Red Bull, 13 h 23 min for a 16 oz Monster and 15 hours for Java Monster. If you want an afternoon can, the small Red Bull is the only one in this comparison that fits an ordinary bedtime.
These are averages. If caffeine tends to linger for you, set the calculator to high sensitivity and every cutoff moves earlier. Falling asleep fine isn't proof the can had no effect: in an at-home study, a large caffeine dose taken 6 hours before bed cut total sleep by more than an hour. For more on why, see energy drinks and sleep.
Is it safe to drink a Monster and a Red Bull in one day?
For healthy adults, the FDA cites 400 mg of caffeine a day as an amount not generally linked to negative effects, and a 16 oz Monster plus a small Red Bull comes to 240 mg. That leaves room for a cup of coffee, but two 16 oz Monsters plus a 16 oz Red Bull (471 mg) goes over.
That guideline is for adults. The FDA notes that medical experts advise against energy drinks for children and teens. If you're pregnant, nursing, have a heart condition or take medications, ask your health care provider about a lower limit. To add up a whole day, see how much caffeine is too much.