Pepsi has more caffeine than Diet Pepsi: 38mg vs 35mg in the same 12 oz can. That is a 3mg gap, and since the cans match, the per-serving number is the whole story.
Pepsi vs Diet Pepsi: the numbers
| Pepsi | Diet Pepsi | |
|---|---|---|
| Caffeine per serving | 38mg per 12 oz can | 35mg per 12 oz can |
| Caffeine per fl oz | 3.2mg | 2.9mg |
| Servings to reach 400mg (FDA context) | 10.5 | 11.4 |
Sources: Pepsi's figure is verified in our Pepsi 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 Pepsi 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
- Pepsi: the full caffeine guide
- Diet Pepsi: the full caffeine guide
- The verified caffeine database
- Every drink compared: the comparisons index
FAQ
Does Pepsi or Diet Pepsi have more caffeine? Pepsi: 38mg per 12 oz can versus 35mg per 12 oz can for Diet Pepsi.
Which is stronger per ounce? Pepsi, at about 3.2mg 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.