The same dose whatever size you order
Starbucks’ London Fog Latte, Earl Grey tea with steamed milk and vanilla syrup, carries 40 mg of caffeine at every size Starbucks sells it: Short, Tall, Grande and Venti alike. Unlike espresso drinks, where a bigger cup means more shots, this drink’s caffeine comes from a fixed amount of tea concentrate, so a Venti is no stronger than a Short, just more milk and ice.
Well below the espresso drinks
A London Fog’s 40 mg is a small fraction of a Grande Caffè Latte (150 mg), and slightly less than a Grande Chai Latte (55 mg), another milk-and-tea drink on the same menu. It matches its base tea exactly, since Starbucks lists 40 mg for brewed Earl Grey too, at every cup size.
A tea latte for the coffee-averse
The London Fog is a common recommendation for someone at a coffee shop who wants a warm, milky drink without much caffeine, or without coffee’s flavour at all. Because the tea concentrate is fixed regardless of size, ordering the smallest available size doesn’t reduce the caffeine the way it would with an espresso drink; the milk-to-tea ratio changes, but the 40 mg dose stays the same.
Where it fits in a day
At 40 mg, even a Venti is far under the 200 mg single dose EFSA assessed as safe for healthy adults. Ten Ventis, 400 mg, would be needed to reach the daily figure the FDA cites for healthy adults. In pregnancy, where ACOG uses a 200 mg daily ceiling, five Ventis still fit under the day’s allowance.