The company said on Tuesday the labels were meant to encourage health-conscious consumers to further customize orders by opting for sugar-free syrups or nonfat milk over more calorie heavy alternatives.
"People are already customizing their drinks," said Lisa Passe, a Starbucks spokeswoman.
She added that the coffee company's pastries will also come with a calorie count.
Starbucks' decision follows moves by Panera Bread Co, the first national restaurant chain to voluntarily post calorie counts, and sandwich chain Subway, which has used the disclosures to position itself as a healthier alternative to its fast-food rivals.
The U.S. Food and Drug Administration is expected to require chains with 20 locations or more to make similar disclosures nationwide by the end of the year. Food chains in New York City and California already post nutritional statistics to comply with local health regulations.
Researchers are split over the effectiveness of the labels in improving public health. One study in New York City, which has mandated the labels for several years, found that calorie postings led one in six customers to notice the information and buy foods with fewer calories.
But researchers at Tufts University found that labels at fast-food restaurants under-reported calories by 7 percent and that 20 percent of the foods surveyed had at least 100 calories more than claimed. The study did not examine drinks.
"There's no measure in the (federal) regulations to address accuracy," said Lorien Urban, one of the scientists who worked on the Tufts study. "It's yet to be determined how that will play out nationwide."
