A Venti size at Starbucks means 20 ounces for hot drinks and 24 ounces for cold drinks. The Venti size is the largest option available at Starbucks and is ideal for those seeking more caffeine or a larger serving. Its important to note that there are variations between the Venti sizes for hot and cold drinks. The Venti hot size is 20 ounces, while the Venti cold size is 24 ounces.