Starbucks Doubleshot Espresso & Cream has more caffeine than Barq's root beer on both counts: 120mg per 6.5 oz can against 22mg per 12 oz can, and about 18mg per fluid ounce against 2. The serving sizes differ, so the table below shows both ways of counting.
These are different categories of drink, which changes how the caffeine arrives. Energy drinks and sodas list an exact number because caffeine is a measured additive; brewed drinks vary with the beans and the brew, so their figures are compiled averages. The numbers here are the standard published values for each.
Barq's root beer vs Starbucks Doubleshot Espresso & Cream: the numbers
| Barq's root beer | Starbucks Doubleshot Espresso & Cream | |
|---|---|---|
| Caffeine per serving | 22mg per 12 oz can | 120mg per 6.5 oz can |
| Caffeine per fl oz | 1.8mg | 18.5mg |
| Servings to reach 400mg (FDA context) | 18.2 | 3.3 |
Sources: Barq's root beer's figure is verified in our Barq's root beer caffeine guide against Coca-Cola brand data (source); Starbucks Doubleshot Espresso & Cream's figure is verified in our Starbucks Doubleshot Espresso & Cream guide against Caffeine Informer / Starbucks nutrition (source).
The concentration gap is the striking part: Starbucks Doubleshot Espresso & Cream packs roughly 10 times the caffeine per ounce. Sipping speed matters at that density; a 6.5 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 Starbucks Doubleshot Espresso & Cream 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
- Barq's root beer: the full caffeine guide
- Starbucks Doubleshot Espresso & Cream: the full caffeine guide
- The verified caffeine database
- Every drink compared: the comparisons index
FAQ
Does Barq's root beer or Starbucks Doubleshot Espresso & Cream have more caffeine? Starbucks Doubleshot Espresso & Cream: 120mg per 6.5 oz can versus 22mg per 12 oz can for Barq's root beer.
Which is stronger per ounce? Starbucks Doubleshot Espresso & Cream, at about 18.5mg 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.