eli5 if something has 7% of alcohol and you drink 2 bottles of it,you don’t consume 14% of alcohol. but if a cookie has 100 calories and you eat two,you consume 200 calories. why?

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Calories are counted as a value.

Alcohol is measured as a fraction of volume, not a volume consumed.

If there are 100mL of a drink which is 7% alcohol, that means there are 7mL of alcohol in it. If you drink two such drinks, you have drank a total of 200mL of liquid, and 14mL of it was alcohol. But what is 14/200? It’s 0.07 or 7%.

Percent is a ratio. It means we don’t need to know the exact value of both items (the alcohol and the total volume). If we know one, we can find the other by using the ratio. But let’s try something that does change like you’re asking. Let’s say you have a few drinks (maybe 3) and your B.A.C jumps from 0 to 0.03% if you drink another 3 drinks, your B.A.C. should jump to about 0.06% this is because you’re adding alcohol to your blood, but you’re not adding (much) more blood. And that’s the denominator of the percent ratio.

For the alcoholic drink, to avoid confusion, let’s just say you’re pouring it into a punch bowl. By pouring one in, you’re adding both water and alcohol so the punch bowl has 7% alcohol in it. If you pour a second drink into the punch bowl you are adding more alcohol (which you would think would make it higher concentration), but you’re also adding more water (which you would think would dilute it) so it cancels out and has the same concentration as before.

Because you are comparing different things. Calories are the amount of “energy” in a food. Alcohol percentage is a measure of how “strong” the drink is.

Alcohol has 7 cal per gram (“energy”) plus all the other sugar, juice and other calories in the drink (more calories in mixed drinks/beers). If you look at the calories of a serving of beer, you could be consuming 150 calories per drink.

Alcohol percentage is a ratio describing how much alcohol is in the drink. That doesn’t change no matter how much of it you drink.

Calorie content is an absolute value which does increase if you eat more.

If you buy two shirts for $5 each, you spend $10. If you buy two shirts at 50% off, you’re not getting them for free.