Ounces in a cup
There are 8 fluid ounces (fl oz) in a cup (C) in the US customary system of measurement. In the imperial system, there are 10 fluid ounces in a cup.
Fluid ounces are not related to the ounce used as a unit of weight or mass. It is not uncommon for fluid ounces to be referred to as just "ounce" but usually only when it is clear that fluid ounces are being referenced. An example of this would be using ounces when talking about a beverage. While it could reference the weight or mass of the beverage, it is not common practice, and most people would likely assume that a fluid ounce is being used, rather than the ounce being a reference to weight.
Ounce to cup conversion
The following converters can be used to convert from ounces to cups or cups to ounces. Just choose whichever system of measurement you would like to use, then enter a value in either ounces or cups to convert between the two.
Ounce to cup conversion explanation
Converting between ounces and cups requires us to remember the relationship between ounces and cups in both the imperial and US customary systems of measurement:
US customary system:
8 fl oz = 1 C
1 fl oz = 
C
Imperial system:
10 fl oz = 1 C
1 fl oz = 
C
To convert from fluid ounces to cups in the US customary system, we divide by 8. To convert from cups to fluid ounces, we multiply by 8. In the imperial system we would divide a value in fluid ounces by 10, and multiply a value in cups by 10 to convert to fluid ounces.
Examples
1. Convert 38 US fluid ounces to US customary cups:
38 fl oz ÷ 8 = 4.75 C
2. Convert 3 imperial cups to imperial fluid ounces:
3 C × 10 = 30 fl oz