US fluid ounce (fl oz)

Definition

A US fluid ounce, one 128th of a gallon (29.5735295625 milliliters).

History

The fluid ounce began as the volume of one ounce of wine or water and later diverged between the US and imperial systems. The US fluid ounce is one 128th of a gallon, about 29.6 milliliters.

Where it is used

Fluid ounces measure drink sizes and recipe liquids in the United States; the imperial fluid ounce used elsewhere is slightly smaller.

Typical uses include drink sizes, recipe liquids.

Conversion pages

These pages convert US fluid ounce to or from another unit in volume.

• US fluid ounce to milliliter

Other Volume units

• Liter (L)
• Milliliter (mL)
• US gallon (gal)
• US quart (qt)
• US pint (pt)
• US cup (cup)
• Tablespoon (tbsp)
• Teaspoon (tsp)
• Cubic meter (m³)
• Cubic foot (ft³)

Sources

• NIST HB 44 NIST Handbook 44, Appendix C §2 (U.S. Customary Units) and §5 (Tables of Equivalents) · Dataset reviewed Nov 11, 2026