Diet Coke has more caffeine than Coca-Cola Zero Sugar: 46mg vs 34mg in the same 12 oz can. That is a 12mg gap, and since the cans match, the per-serving number is the whole story.
Coca-Cola Zero Sugar vs Diet Coke: the numbers
| Coca-Cola Zero Sugar | Diet Coke | |
|---|---|---|
| Caffeine per serving | 34mg per 12 oz can | 46mg per 12 oz can |
| Caffeine per fl oz | 2.8mg | 3.8mg |
| Servings to reach 400mg (FDA context) | 11.8 | 8.7 |
Sources: Coca-Cola Zero Sugar's figure is verified in our Coca-Cola Zero Sugar 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 Coca-Cola Zero Sugar 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
- Coca-Cola Zero Sugar: the full caffeine guide
- Diet Coke: the full caffeine guide
- The verified caffeine database
- Every drink compared: the comparisons index
- Compare any two of 120+ drinks
FAQ
Does Coca-Cola Zero Sugar or Diet Coke have more caffeine? Diet Coke: 46mg per 12 oz can versus 34mg per 12 oz can for Coca-Cola Zero Sugar.
Which is stronger per ounce? Diet Coke, at about 3.8mg per fluid ounce versus 2.8mg for Coca-Cola Zero Sugar.
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