Eight ounces is equal to one cup.
Secondly, is a cup always 8 ounces? — a cup of water happens to equal both 8 fluid ounces (in volume) and 8 ounces (in weight), so you might naturally assume that 1 cup equals 8 ounces of weight universally in recipes. Since fluid ounces and ounces are measuring such very different things, they are rarely the same for most ingredients.
Secondly, how do you measure out 8 ounces?
Liquid measuring cups indicate that 1 cup = 8 ounces. But what they really mean is 1 cup of liquid = 8 fluid ounces.
How big is an 8 oz glass?
The size of an 8-ounce glass is dependent on the style of the glass, but each glass has the volume capable of holding 8 fluid ounces, 1 cup or 236.5 mL. If stated to be an 8-ounce glass then it is a relatively small drinking cup.