A US customary cup is 236.5882365 milliliters.
Cups to Fluid ounces Converter — cup to fl oz
Convert Cup (cup) to Fluid ounce (fl oz) using the exact conversion factor (1 cup = 8 fluid ounce). See the formula, worked examples, conversion table, unit comparison, history, and common uses.
Cups to Fluid ounces converter
Converter
Cooking Converter
Convert cooking volume and mass units used in recipes and nutrition workflows.
Context values
Some unit families need one extra value for a physically accurate result.
A US fluid ounce is 1/128 of a US gallon.
Result = input x 0.0002365882365 / 2.95735296e-5.
Volume units are compatible.
Reserved above the conversion cards and below the converter.
About Converting Cups to Fluid ounces
Cup and Fluid ounce both show up in recipes, and converting between them matters whenever a recipe from one country's cookbook needs to be followed with another country's measuring tools. Cup is typically associated with united States (recipes and cooking measurement), while Fluid ounce is typically associated with united States (beverage, nutrition labeling).
Formula
fluid ounces = cups × 8
This factor comes from each unit's defined relationship to the category's base unit: 1 cup equals 0.0002365882365 base units, and 1 fluid ounce equals 0.0000295735295625 base units, so dividing one by the other gives the direct cup-to-fluid ounce factor of 8.
Simple example
1 cup × 8 = 8 fl oz
1 cup = 8 fluid ounces.
Real-world example
2 cup × 8 = 16 fl oz
2 cups = 16 fluid ounces.
Conversion table
| Cup (cup) | Fluid ounce (fl oz) |
|---|---|
| 0.25 cup | 2 fl oz |
| 0.5 cup | 4 fl oz |
| 1 cup | 8 fl oz |
| 2 cup | 16 fl oz |
| 4 cup | 32 fl oz |
| 8 cup | 64 fl oz |
Reverse conversion: Fluid ounce to Cup
8 fl oz × 0.125 = 1 cup
8 fluid ounces = 1 cup.
cups = fluid ounces × 0.125
For a page dedicated to this direction, see Fluid ounce to Cup.
Cup vs. Fluid ounce
| Aspect | Cup | Fluid ounce |
|---|---|---|
| Family | US customary unit (culinary) | US customary unit |
| Typical use | US recipe and cooking measurement | US beverage container sizing (soda, water bottles) |
| Where it's used | United States (recipes and cooking measurement) | United States (beverage, nutrition labeling) |
Understanding the Cup
Cup (cup) measures volume. The US customary cup used in cooking is defined as exactly 240 milliliters (a rounded culinary standard, not the older 236.588 mL legal cup). It is classified as a US customary unit (culinary).
Where it's used: United States (recipes and cooking measurement)
Cooking cup vs. legal US cup. US recipes commonly round the cup to 240 mL for convenience, while the precise legal US cup (used to derive fluid ounces, pints, etc.) is 236.588 mL — a small but sometimes noticeable difference in precise baking.
Uses of the Cup today
- US recipe and cooking measurement
- Nutrition labeling serving sizes
- Baking, where volume-based flour/sugar measurement is still common in the US
History of the Cup
The cup as a cooking measure grew out of household and community cookbook conventions in 19th-century America, standardizing what had been ad hoc measurements ('a teacup of flour') into a fixed volume.
The US FDA uses a rounded 240 mL 'metric cup' for nutrition labeling purposes, distinct from the slightly smaller legal/customary cup (236.588 mL, exactly 1/16 of a US gallon) used elsewhere.
Historical origin. Cup was not the invention of a single named person; it developed through the process described above.
Understanding the Fluid ounce
Fluid ounce (fl oz) measures volume. The US fluid ounce is 1/128 of a US gallon: exactly 29.5735295625 milliliters. It is classified as a US customary unit.
Where it's used: United States (beverage, nutrition labeling)
Uses of the Fluid ounce today
- US beverage container sizing (soda, water bottles)
- US nutrition and medication dosing labels
History of the Fluid ounce
The US fluid ounce follows from the same English wine-gallon system as the rest of the US liquid volume units, defined as a consistent fraction of the gallon.
Historical origin. Fluid ounce was not the invention of a single named person; it developed through the process described above.
Cup — sources
- US FDA — Reference Amounts Customarily Consumed — Uses the 240 mL rounded cup for nutrition labeling.
Fluid ounce — sources
- NIST Handbook 44, Appendix C — General tables of units including the US fluid ounce definition.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many fluid ounces are in 1 cup?
1 cup equals 8 fluid ounces, using the exact defined conversion factor rather than an estimate.
How do I convert cup to fluid ounce?
Multiply the cup value by 8. The converter above does this instantly to whatever precision you set.
How do I convert fluid ounce back to cup?
Use the reverse factor: 1 fluid ounce equals 0.125 cups. You can also use the swap control in the converter above to flip the direction instantly.
What is a cup?
Cup (cup) measures volume. The US customary cup used in cooking is defined as exactly 240 milliliters (a rounded culinary standard, not the older 236.588 mL legal cup). It is classified as a US customary unit (culinary).
What is a fluid ounce?
Fluid ounce (fl oz) measures volume. The US fluid ounce is 1/128 of a US gallon: exactly 29.5735295625 milliliters. It is classified as a US customary unit.
Is the cup to fluid ounce conversion exact?
Yes. The US fluid ounce is 1/128 of a US gallon: exactly 29.5735295625 milliliters. That fixed definition is what the converter above uses, so any rounding you see is a display choice, not a limitation of the math.
What is the difference between cooking cup vs. legal us cup?
US recipes commonly round the cup to 240 mL for convenience, while the precise legal US cup (used to derive fluid ounces, pints, etc.) is 236.588 mL — a small but sometimes noticeable difference in precise baking.
Where is the cup still used today?
United States (recipes and cooking measurement)