Monster Ultra (Zero Ultra) carries more total caffeine per serving (150mg per 16 oz can vs 80mg per 8.4 oz can), but ounce for ounce Red Bull is actually the stronger drink at about 10mg per fluid ounce against 9. Which one "has more caffeine" depends on whether you measure the container or the concentration.
Monster Ultra (Zero Ultra) vs Red Bull: the numbers
| Monster Ultra (Zero Ultra) | Red Bull | |
|---|---|---|
| Caffeine per serving | 150mg per 16 oz can | 80mg per 8.4 oz can |
| Caffeine per fl oz | 9.4mg | 9.5mg |
| Servings to reach 400mg (FDA context) | 2.7 | 5.0 |
Sources: Monster Ultra (Zero Ultra)'s figure is verified in our Monster Ultra (Zero Ultra) caffeine guide against Caffeine Informer (source); Red Bull's figure is verified in our Red Bull guide against Red Bull label / Caffeine Informer (source).
Which one should you pick?
Pick Red Bull when you want the lighter dose or a slower ramp, and Monster Ultra (Zero Ultra) when you actually need the bigger hit and know your tolerance. If you are stacking either with other caffeinated drinks through the day, run the math against the 400mg reference rather than guessing.
For context, the FDA cites 400mg of caffeine a day as an amount generally not associated with negative effects in healthy adults. Tolerance and health vary, so treat these numbers as information, not advice.
Related reading
- Monster Ultra (Zero Ultra): the full caffeine guide
- Red Bull: the full caffeine guide
- The verified caffeine database
- Every drink compared: the comparisons index
- Compare any two of 120+ drinks
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Gear from this guide
FAQ
Does Monster Ultra (Zero Ultra) or Red Bull have more caffeine? Monster Ultra (Zero Ultra): 150mg per 16 oz can versus 80mg per 8.4 oz can for Red Bull.
Which is stronger per ounce? Red Bull, at about 9.5mg per fluid ounce versus 9.4mg for Monster Ultra (Zero Ultra).
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