My math's fine. I think you misunderstood my post. I was just considering metric and imperial sizes thus included both sets of units.

The first reply to your post shows the math.

Even the 'increased' 240mg in the energy drink is just equivalent to 'regular' coffee due to it being 16oz/473mL can.

As I said though. Much easier to gulp down half a litre of sugary soda than half a litre of oily thick espresso.

I did misunderstand it, my apologies.

According to Google (which cites USDA) for "espresso caffeine" and "coffee caffeine", there is 64 mg of caffeine in 1 fl oz of espresso and 94 mg of caffeine in 8 fl oz of coffee.

So per unit volume, the espresso has several times the caffeine (and you would already expect a double espresso to have more total caffeine than a modest sized drip coffee).