Diet Coke has more caffeine than RC Cola: 46mg vs 43mg in the same 12 oz can. That is a 3mg gap, and since the cans match, the per-serving number is the whole story.
RC Cola vs Diet Coke: the numbers
| RC Cola | Diet Coke | |
|---|---|---|
| Caffeine per serving | 43mg per 12 oz bottle | 46mg per 12 oz can |
| Caffeine per fl oz | 3.6mg | 3.8mg |
| Servings to reach 400mg (FDA context) | 9.3 | 8.7 |
Sources: RC Cola's figure is verified in our RC Cola 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 RC Cola 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
- RC Cola: 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
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Gear from this guide
FAQ
Does RC Cola or Diet Coke have more caffeine? Diet Coke: 46mg per 12 oz can versus 43mg per 12 oz bottle for RC Cola.
Which is stronger per ounce? Diet Coke, at about 3.8mg per fluid ounce versus 3.6mg for RC Cola.
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