High Brew Double Espresso has more caffeine than Diet Coke on both counts: 140mg per 8 oz can against 46mg per 12 oz can, and about 18mg per fluid ounce against 4. 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.
Diet Coke vs High Brew Double Espresso: the numbers
| Diet Coke | High Brew Double Espresso | |
|---|---|---|
| Caffeine per serving | 46mg per 12 oz can | 140mg per 8 oz can |
| Caffeine per fl oz | 3.8mg | 17.5mg |
| Servings to reach 400mg (FDA context) | 8.7 | 2.9 |
Sources: Diet Coke's figure is verified in our Diet Coke caffeine guide against Caffeine Informer (source); High Brew Double Espresso's figure is verified in our High Brew Double Espresso guide against Caffeine Informer (source).
The concentration gap is the striking part: High Brew Double Espresso packs roughly 5 times the caffeine per ounce. Sipping speed matters at that density; a 8 oz can finished in minutes hits differently than the same milligrams spread over a slow cup.
Which one should you pick?
Pick Diet Coke when you want the lighter dose or a slower ramp, and High Brew Double Espresso 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
- Diet Coke: the full caffeine guide
- High Brew Double Espresso: the full caffeine guide
- The verified caffeine database
FAQ
Does Diet Coke or High Brew Double Espresso have more caffeine? High Brew Double Espresso: 140mg per 8 oz can versus 46mg per 12 oz can for Diet Coke.
Which is stronger per ounce? High Brew Double Espresso, at about 17.5mg per fluid ounce versus 3.8mg for Diet Coke.
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.