How heavy and how thick must a steak "Chateaubriand" be?

An average chateaubriand steak is the thickness of a small roast, weighs approximately 12-16 oz (340.19-453.59 grams) and is traditionally prepared for two servings.

http://www.wisegeek.com/what-is-chateaubriand.htm

Châteaubriand is a small roast extravagantly cut from the center of the beef tenderloin. In the 200 years since it was first prepared by the Vicomte de Châteaubriand's chef, Montmireil, we seem to have lost its exact dimensions. Some people will tell you that it can be as little as 1-1/2 inches thick, which is essentially a tenderloin steak, and not châteaubriand. There is even disagreement in really old cookbooks, though, in which the meat ranges from three to five inches thick, and weighs 12 to 16 ounces. It should serve two to three.

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