How much alcohol in one capful of rum?

There is no standard size for a "capful" of rum, so the amount of alcohol in one capful can vary depending on the brand and type of rum. For example, a capful of Bacardi Superior White Rum contains about 0.5 fluid ounces (15 milliliters) of alcohol, while a capful of Captain Morgan Original Spiced Rum contains about 0.6 fluid ounces (18 milliliters) of alcohol.