Mountain Dew has more caffeine than Diet Pepsi: 54mg vs 35mg in the same 12 oz can. That is a 19mg gap, and since the cans match, the per-serving number is the whole story.
Mountain Dew vs Diet Pepsi: the numbers
| Mountain Dew | Diet Pepsi | |
|---|---|---|
| Caffeine per serving | 54mg per 12 oz can | 35mg per 12 oz can |
| Caffeine per fl oz | 4.5mg | 2.9mg |
| Servings to reach 400mg (FDA context) | 7.4 | 11.4 |
Sources: Mountain Dew's figure is verified in our Mountain Dew caffeine guide against Caffeine Informer (source); Diet Pepsi's figure is verified in our Diet Pepsi guide against Caffeine Informer (source).
Which one should you pick?
Pick Diet Pepsi when you want the lighter dose or a slower ramp, and Mountain Dew 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
- Mountain Dew: the full caffeine guide
- Diet Pepsi: the full caffeine guide
- The verified caffeine database
- Every drink compared: the comparisons index
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Gear from this guide
FAQ
Does Mountain Dew or Diet Pepsi have more caffeine? Mountain Dew: 54mg per 12 oz can versus 35mg per 12 oz can for Diet Pepsi.
Which is stronger per ounce? Mountain Dew, at about 4.5mg per fluid ounce versus 2.9mg for Diet Pepsi.
Comparing caffeine? The caffeine comparison tool puts hundreds of drinks side by side, and the caffeine curfew calculator can check your cutoff time for tonight.
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