C4 Smart Energy has more caffeine than Aspire Energy on both counts: 200mg per 16 oz can against 80mg per 12 oz can, and about 12mg per fluid ounce against 7. The serving sizes differ, so the table below shows both ways of counting.
Aspire Energy vs C4 Smart Energy: the numbers
| Aspire Energy | C4 Smart Energy | |
|---|---|---|
| Caffeine per serving | 80mg per 12 oz can | 200mg per 16 oz can |
| Caffeine per fl oz | 6.7mg | 12.5mg |
| Servings to reach 400mg (FDA context) | 5.0 | 2.0 |
Sources: Aspire Energy's figure is verified in our Aspire Energy caffeine guide against Aspire / Caffeine Informer (source); C4 Smart Energy's figure is verified in our C4 Smart Energy guide against Cellucor / Caffeine Informer (source).
Which one should you pick?
Pick Aspire Energy when you want the lighter dose or a slower ramp, and C4 Smart Energy 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
- Aspire Energy: the full caffeine guide
- C4 Smart Energy: 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 Aspire Energy or C4 Smart Energy have more caffeine? C4 Smart Energy: 200mg per 16 oz can versus 80mg per 12 oz can for Aspire Energy.
Which is stronger per ounce? C4 Smart Energy, at about 12.5mg per fluid ounce versus 6.7mg for Aspire Energy.
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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