For some reason, "Short" coffees are neither promoted nor advertised by Starbucks. However, the caffeine content of this particular brewed coffee is take as a proportion of samples taken from Starbucks Breakfast Blend coffee (see the Grande version for the full story).

The caffeine levels vary greatly between blends and even individual coffees served. the value above is from Starbucks.

However a slightly higher amount (186mg) can be averaged from 6 different samples that were caffeine tested.

Factors such as coffee bean variety, roasting method, grind size, and length of brewing time all play a part in altering caffeine content.