4 ounces or a half cup....or did you mean how much fat? calories? fun?
I so dislike recipes which give butter equivalents in sticks. Or cups or fractions thereof. Ick. A pound of butter weighs, or equals, 16 ounces. A pound of butter divided into 4 sticks, or quarters, equals 4 sticks, or quarters of 4 ounces each. 4 ounces times 4 equals 16 ounces, or 1 pound. That given, one "stick" of butter is equal to 4 ounces.
You may also be looking for the equivalent in grams. In the US, one stick is easily understood as 1/2 cup which also means 4 oz or 8 tbsp or 113.5 grams. 2 sticks is one cup or 8 oz or 16 tbsp or 227 grams.
A French chef's "pat" (of butter).
I'm with Cynthia on this. I buy Plugra or Kerrygold, so even though I never buy butter in sticks, I'm forever having to remember how many ounces are in one so I can calculate the equivalent.