Mountain Dew Zero Sugar has more caffeine than Barq's root beer: 68mg vs 22mg in the same 12 oz can. That is a 46mg gap, and since the cans match, the per-serving number is the whole story.
Mountain Dew Zero Sugar vs Barq's root beer: the numbers
| Mountain Dew Zero Sugar | Barq's root beer | |
|---|---|---|
| Caffeine per serving | 68mg per 12 oz can | 22mg per 12 oz can |
| Caffeine per fl oz | 5.7mg | 1.8mg |
| Servings to reach 400mg (FDA context) | 5.9 | 18.2 |
Sources: Mountain Dew Zero Sugar's figure is verified in our Mountain Dew Zero Sugar caffeine guide against PepsiCo product facts (source); Barq's root beer's figure is verified in our Barq's root beer guide against Coca-Cola brand data (source).
The concentration gap is the striking part: Mountain Dew Zero Sugar packs roughly 3 times the caffeine per ounce. Sipping speed matters at that density; a 12 oz can finished in minutes hits differently than the same milligrams spread over a slow cup.
Which one should you pick?
Pick Barq's root beer when you want the lighter dose or a slower ramp, and Mountain Dew Zero Sugar 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
- Mountain Dew Zero Sugar: the full caffeine guide
- Barq's root beer: the full caffeine guide
- The verified caffeine database
FAQ
Does Mountain Dew Zero Sugar or Barq's root beer have more caffeine? Mountain Dew Zero Sugar: 68mg per 12 oz can versus 22mg per 12 oz can for Barq's root beer.
Which is stronger per ounce? Mountain Dew Zero Sugar, at about 5.7mg per fluid ounce versus 1.8mg for Barq's root beer.
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.