A quarter cup is how many Ounces?

For liquid ingredients, such as water, milk, or oil:

1 cup = 8 fluid ounces (fl oz)
1/2 cup = 4 fl oz
1/4 cup = 2 fl oz

For dry ingredients, such as flour, sugar, or cereal:

1 cup = 8-16 ounces (depending on density)
1/2 cup = 4-8 ounces
1/4 cup = 2-4 ounces (approximately 2.25-2.5 ounces for most dry ingredients)

Keep in mind that the exact conversion for dry ingredients may vary depending on how the ingredient is packed and its density.