Lighter than a hot cup, size for size
Starbucks’ Iced Black Tea carries 20 to 25 mg in a Tall, 25 to 30 mg in a Grande, 40 to 45 mg in a Venti, and 55 to 60 mg in a Trenta. That’s notably lighter per ounce than its own hot brewed teas, which hold a flat 40 mg at every size, and lighter than home-brewed iced tea, which USDA puts at about 72 mg for a 12 oz glass; Starbucks’ iced tea is brewed to be served over ice rather than a full-strength brew simply chilled.
Matched by the green tea version
Starbucks’ Iced Green Tea publishes the identical ranges at every size, 20 to 25 mg in a Tall up to 55 to 60 mg in a Trenta, so the choice between the two comes down to taste rather than caffeine.
Requesting the tea steeped stronger, or extra tea bags, isn’t a standard modification the way an extra espresso shot is, so these published figures are the reliable ones to work from rather than an estimate based on taste.
Where it fits in a day
At up to 30 mg, a Grande is far under the 200 mg single dose EFSA assessed as safe for healthy adults. Even a Trenta at the top of its range, 60 mg, is a small fraction of the 400 mg daily figure the FDA cites. In pregnancy, where ACOG uses a 200 mg daily ceiling, several Grandes a day still fit comfortably.