Starbucks: In a Latte Trouble ... You're Shorting Our Coffee!!

Two Cali java fanatics have a bean to grind with Starbucks for refusing to fill their cups to the rim ... according to a new suit.

The duo says every time they order a tall, grande or venti sized latte ... it's grossly underfilled. They point out the menu promises 12, 16 and 20 ounces -- but based on their research Starbucks underfills those cups by about 25% EVERY time.

In the class action suit, they admit occasionally the milk foam on top gets to the rim, but they add ... "In the food science community, as well as in the weights and measures community, foam is not measured on a volumetric basis."

Translation: Foam doesn't count!

Nor do they think this is an accident ... they paint CEO Howard Schultz as the villain for cutting costs by reducing the amount of milk in each latte.

They're seeking damages for Starbucks latte drinkers all across the country.