There are 8 fluid ounces in one cup. One fluid ounce is equivalent to one-eighth of a cup and is a measure of volume as opposed to an ounce, which is a measure of weight.
Fluid ounces are an imperial measurement. The metric equivalent of a fluid ounce is a milliliter. There are 235 ml in a cup. In cooking and baking, it is important when measuring ingredients to use a uniform method for quantities. It is entirely acceptable to use cups, fluid ounces or ounces, as most recipes call for relative amounts of ingredients, for example, half as much fat as flour.