Mountain Dew Zero Sugar has more caffeine than A&W Root Beer: 68mg vs 0mg in the same 12 oz can. That is a 68mg gap, and since the cans match, the per-serving number is the whole story.
Mountain Dew Zero Sugar vs A&W Root Beer: the numbers
| Mountain Dew Zero Sugar | A&W Root Beer | |
|---|---|---|
| Caffeine per serving | 68mg per 12 oz can | 0mg per 12 oz can |
| Caffeine per fl oz | 5.7mg | 0.0mg |
| Servings to reach 400mg (FDA context) | 5.9 | n/a (caffeine-free) |
Sources: Mountain Dew Zero Sugar's figure is verified in our Mountain Dew Zero Sugar caffeine guide against PepsiCo product facts (source); A&W Root Beer's figure is verified in our A&W Root Beer guide against Caffeine Informer (source).
The concentration gap is the striking part: Mountain Dew Zero Sugar packs roughly 567 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 A&W 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
- A&W Root Beer: the full caffeine guide
- The verified caffeine database
FAQ
Does Mountain Dew Zero Sugar or A&W Root Beer have more caffeine? Mountain Dew Zero Sugar: 68mg per 12 oz can versus 0mg per 12 oz can for A&W Root Beer.
Which is stronger per ounce? Mountain Dew Zero Sugar, at about 5.7mg per fluid ounce versus 0.0mg for A&W 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.