How much caffeine is there in a latte?
A Starbucks Tall latte (12oz) is made with a single shot of espresso which contains 75mg of caffeine. A hot Grande latte (16oz) or a hot Venti latte (20oz) with 2 shots of espresso would contain 150mg total of caffeine.
If you are visiting a specialty coffee shop, an espresso drink usually contains a double shot of espresso. A typical 12oz latte with a double shot of espresso contains about 150mg of caffeine.
As I always mention, these numbers are averages and still just approximations. Coffee is a natural product, and 20 grams of ground coffee may not always contain the same amount of caffeine. Different cafes use different beans, and that can affect the amount of caffeine. Also, in a specialty cafe, there is a lot more room for variation as each shot is pulled by a barista and the espresso output could vary a bit. The time and length of the shot can vary – this will affect the extraction percentage which in turn will affect caffeine content.