A cup flour weighs in at 4 and 1/4 ounces.
If you're baking or making other recipes then I would recommend getting a good digital scale and weigh the ingredients to ensure the proper amount.
I always use a digital scale to weigh ingredients including flour because sometimes a recipe tells me how much ingredients in weight instead of in cups or ounces for some reason.
But when I weigh a cup of flour it comes out to 4 and 1/4 ounces.
In one fluid once there are 8 ounces in a fluid ounce of a cup but for dry ingredients a cup weighs just over 4 ounces.