Tall (12 oz.) is the smallest Starbucks coffee size on the standard menu. Tall espresso drinks, such as lattes, mochas, and macchiatos, come with a single shot of espresso unless you indicate otherwise—so they have the same amount of caffeine as the short, but with extra milk or another non-caffeinated beverage. A tall coffee is equal to two cups of regular six-ounce coffee.
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You'll get 16 fluid ounces of any hot or cold beverage when you order a grande. Starbucks' Grande espresso beverages have two shots of espresso and are the equal of two and a half (six-ounce) cups of coffee.
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A venti hot is 20 ounces, which is little more than three (six-ounce) cups of coffee, and a venti cold is 24 ounces. Because cold drinks include ice (unless otherwise specified), venti cold is larger than venti hot.