One-third cup of butter is equal to 5 1/3 tablespoons. One teaspoon is equal to 1/3 tablespoon, so the measurement is 5 tablespoons and 1 teaspoon of butter. These measurements are the same for butter as for other materials like flour or milk.
When measuring by weight, 1 tablespoon of butter weighs 14 grams or 1/2 ounce. This means that 1/3 cup of butter weighs about 74.67 grams or 2.67 ounces. A standard U.S. stick of butter has 8 tablespoons in it, and the wrappers usually have measuring marks printed on them for each tablespoon, 1/4 cup, 1/3 cup and 1/2 cup of butter.