A US fluid ounce is 1/128 of a US gallon.
Fluid ounces to Cups Converter — fl oz to cup
Convert Fluid ounce (fl oz) to Cup (cup) using the exact conversion factor (1 fluid ounce = 0.125 cup). See the formula, worked examples, conversion table, unit comparison, history, and common uses.
Fluid ounces to Cups converter
Converter
Volume Converter
Convert metric, US customary, imperial, cooking, dry, and industrial volume units.
Context values
Some unit families need one extra value for a physically accurate result.
A US customary cup is 236.5882365 milliliters.
Result = input x 2.95735296e-5 / 0.0002365882365.
Volume uses the cubic meter as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Fluid ounces to Cups
Fluid ounce and Cup appear side by side at fuel pumps and on beverage labels, since the US measures liquids in gallons while most of the world uses liters. Fluid ounce is typically associated with united States (beverage, nutrition labeling), while Cup is typically associated with united States (recipes and cooking measurement).
Formula
cups = fluid ounces × 0.125
This factor comes from each unit's defined relationship to the category's base unit: 1 fluid ounce equals 0.0000295735295625 base units, and 1 cup equals 0.0002365882365 base units, so dividing one by the other gives the direct fluid ounce-to-cup factor of 0.125.
Simple example
1 fl oz × 0.125 = 0.125 cup
1 fluid ounce = 0.125 cups.
Real-world example
10 fl oz × 0.125 = 1.25 cup
10 fluid ounces = 1.25 cups.
Conversion table
| Fluid ounce (fl oz) | Cup (cup) |
|---|---|
| 1 fl oz | 0.125 cup |
| 5 fl oz | 0.625 cup |
| 10 fl oz | 1.25 cup |
| 25 fl oz | 3.125 cup |
| 50 fl oz | 6.25 cup |
| 100 fl oz | 12.5 cup |
Reverse conversion: Cup to Fluid ounce
0.125 cup × 8 = 1 fl oz
0.125 cups = 1 fluid ounce.
fluid ounces = cups × 8
For a page dedicated to this direction, see Cup to Fluid ounce.
Fluid ounce vs. Cup
| Aspect | Fluid ounce | Cup |
|---|---|---|
| Family | US customary unit | US customary unit (culinary) |
| Typical use | US beverage container sizing (soda, water bottles) | US recipe and cooking measurement |
| Where it's used | United States (beverage, nutrition labeling) | United States (recipes and cooking measurement) |
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.
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.
Fluid ounce — sources
- NIST Handbook 44, Appendix C — General tables of units including the US fluid ounce definition.
Cup — sources
- US FDA — Reference Amounts Customarily Consumed — Uses the 240 mL rounded cup for nutrition labeling.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many cups are in 1 fluid ounce?
1 fluid ounce equals 0.125 cups, using the exact defined conversion factor rather than an estimate.
How do I convert fluid ounce to cup?
Multiply the fluid ounce value by 0.125. The converter above does this instantly to whatever precision you set.
How do I convert cup back to fluid ounce?
Use the reverse factor: 1 cup equals 8 fluid ounces. You can also use the swap control in the converter above to flip the direction instantly.
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.
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).
Is the fluid ounce to cup conversion exact?
Yes. 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). 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 fluid ounce still used today?
United States (beverage, nutrition labeling)