Cups to Fluid Ounces Converter
Convert US cups to US fluid ounces (fl oz)
Cup (US)
Definition: The US cup is a unit of volume used primarily in cooking and baking. One US cup is defined as exactly 8 US fluid ounces, making this one of the simplest and most exact volume conversions in the US customary system. It is half a US pint and one-sixteenth of a US gallon.
History/origin: The US cup was standardized as exactly 8 fluid ounces, a definition that has remained consistent since the late 19th century. The clean 8:1 ratio between cups and fluid ounces is what makes this conversion so practical — a standard 8 fl oz glass of water is exactly one cup, and a 16 fl oz water bottle is exactly two cups.
Current use: The US cup is the primary volume measurement in American cooking and baking recipes. Converting cups to fluid ounces is useful when measuring liquids with a fluid ounce-marked measuring cup or bottle, when following beverage recipes, or when comparing US recipe measurements to labeled bottle sizes.
Fluid Ounce (US)
Definition: The US fluid ounce is a unit of volume equal to 1/8 of a US cup or 1/128 of a US gallon. One US fluid ounce equals approximately 29.5735 milliliters. It is important to distinguish fluid ounces (volume) from avoirdupois ounces (weight/mass), as they are entirely different measurements.
History/origin: The fluid ounce was originally defined as the volume of one avoirdupois ounce of water. The US fluid ounce was standardized as 1/128 of a US gallon in 1832. Note that the US fluid ounce (29.57 mL) is slightly larger than the UK/Imperial fluid ounce (28.41 mL), so international recipe conversions should account for this difference.
Current use: The US fluid ounce is widely used on beverage container labels (water bottles, juice, soda, coffee cups), in cooking and baking recipes for small liquid measurements, and in the food service industry for portion sizing. Common reference points: a standard shot is 1.5 fl oz, a can of soda is 12 fl oz, and a standard water bottle is 16.9 fl oz (just over 2 cups).
Cups to Fluid Ounces Conversion Table
| Cups | Fluid Ounces [fl oz] |
|---|---|
| ⅛ cup | 1 fl oz |
| ¼ cup | 2 fl oz |
| ⅓ cup | 2.667 fl oz |
| ½ cup | 4 fl oz |
| ⅔ cup | 5.333 fl oz |
| ¾ cup | 6 fl oz |
| 1 cup | 8 fl oz |
| 1.5 cups | 12 fl oz |
| 2 cups | 16 fl oz |
| 3 cups | 24 fl oz |
| 4 cups | 32 fl oz |
How to Convert Cups to Fluid Ounces
Formula:
1 cup = 8 fl oz (exact)
1 fl oz = 0.125 cups = ⅛ cup
Quick Mental Math:
Multiply cups by 8
This is an exact conversion — one of the easiest in the kitchen!
Useful Relationships:
1 cup = 8 fl oz = 16 tbsp = 48 tsp = 236.588 mL
½ cup = 4 fl oz (standard small juice serving)
1.5 cups = 12 fl oz (standard can of soda)
2 cups = 16 fl oz (standard water bottle)
4 cups = 32 fl oz (large water bottle / quart)
Examples:
Convert 1 cup to fluid ounces:
1 cup × 8 = 8 fl oz
This is 8 fluid ounces (a standard drinking glass of water)
Convert ¾ cup to fluid ounces:
0.75 cups × 8 = 6 fl oz
This is 6 fluid ounces (common in baking recipes)
Convert 2.5 cups to fluid ounces:
2.5 cups × 8 = 20 fl oz
This is 20 fluid ounces (useful for large beverage or soup recipes)