Diet Coke has more caffeine than Diet Pepsi: 46mg vs 35mg in the same 12 oz can. That is a 11mg gap, and since the cans match, the per-serving number is the whole story.
Diet Pepsi vs Diet Coke: the numbers
| Diet Pepsi | Diet Coke | |
|---|---|---|
| Caffeine per serving | 35mg per 12 oz can | 46mg per 12 oz can |
| Caffeine per fl oz | 2.9mg | 3.8mg |
| Servings to reach 400mg (FDA context) | 11.4 | 8.7 |
Sources: Diet Pepsi's figure is verified in our Diet Pepsi caffeine guide against Caffeine Informer (source); Diet Coke's figure is verified in our Diet Coke guide against Caffeine Informer (source).
Which one should you pick?
Pick Diet Pepsi when you want the lighter dose or a slower ramp, and Diet Coke 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
- Diet Pepsi: the full caffeine guide
- Diet Coke: the full caffeine guide
- The verified caffeine database
- Every drink compared: the comparisons index
FAQ
Does Diet Pepsi or Diet Coke have more caffeine? Diet Coke: 46mg per 12 oz can versus 35mg per 12 oz can for Diet Pepsi.
Which is stronger per ounce? Diet Coke, at about 3.8mg 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.