Diet Coke has more caffeine than Coca-Cola Classic: 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.
Diet Coke vs Coca-Cola Classic: the numbers
| Diet Coke | Coca-Cola Classic | |
|---|---|---|
| Caffeine per serving | 46mg per 12 oz can | 34mg per 12 oz can |
| Caffeine per fl oz | 3.8mg | 2.8mg |
| Servings to reach 400mg (FDA context) | 8.7 | 11.8 |
Sources: Diet Coke's figure is verified in our Diet Coke caffeine guide against Caffeine Informer (source); Coca-Cola Classic's figure is verified in our Coca-Cola Classic guide against Caffeine Informer (source).
Which one should you pick?
Pick Coca-Cola Classic 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 Coke: the full caffeine guide
- Coca-Cola Classic: the full caffeine guide
- The verified caffeine database
- Every drink compared: the comparisons index
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Gear from this guide
FAQ
Does Diet Coke or Coca-Cola Classic have more caffeine? Diet Coke: 46mg per 12 oz can versus 34mg per 12 oz can for Coca-Cola Classic.
Which is stronger per ounce? Diet Coke, at about 3.8mg per fluid ounce versus 2.8mg for Coca-Cola Classic.
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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