The same dose iced or hot
Starbucks’ Iced Matcha Latte carries 40 mg of caffeine in a Tall, 65 mg in a Grande, and 85 mg in the 24 oz iced Venti, matching the hot Matcha Latte at every size. Because matcha is whisked whole-leaf powder rather than steeped and strained tea, more of the leaf’s caffeine ends up in the cup than with a typical brewed tea; a Grande’s 65 mg is more than double an 8 oz cup of home-brewed green tea, which USDA puts at about 29 mg.
Stronger than most tea drinks, far below coffee
Among Starbucks’ iced tea-based drinks, matcha runs a little ahead of the Iced Chai Latte (60 mg in a Grande) and well ahead of Iced Black Tea (25 to 30 mg). It remains a small fraction of a Grande Caffè Latte (150 mg).
Whole-leaf tea, not an extract
Matcha’s higher caffeine relative to steeped tea comes down to how it’s made: the whole tea leaf is ground into a fine powder and whisked directly into the drink, rather than steeped in hot water and removed. That means everything in the leaf, caffeine included, ends up in the cup, instead of only whatever the water manages to extract during a short steep.
Where it fits in a day
At 65 mg, a Grande is far under the 200 mg single dose EFSA assessed as safe for healthy adults. Six Grandes, 390 mg, would be needed to approach the 400 mg daily figure the FDA cites. In pregnancy, where ACOG uses a 200 mg daily ceiling, three Grandes still fit comfortably under it.