Fluid Ounce (fl oz)

A US customary unit of volume equal to 1/128 of a gallon

The Fluid Ounce (fl oz) is a unit of volume that developed alongside the needs of commerce, cooking, and chemistry. Volume measurement was crucial for trade in liquids like wine, oil, and grain, leading to a profusion of regional standards that varied even between neighboring towns. The metric system's liter and its multiples brought standardization to most of the world, though the US customary volume system of cups, pints, quarts, and gallons persists in American cooking and everyday use. The Fluid Ounce belongs to one of these traditions.

Accurate volume measurement is critical in engineering, science, commerce, and everyday life. Using the correct unit and applying conversions precisely prevents errors that can be costly or dangerous in professional applications.

Conversion Table

UnitSymbol1 fl oz =
LiterL0.0295735 L
MillilitermL29.5735 mL
Gallon (US)gal0.0078125 gal
Cupcup0.125 cup
Tablespoontbsp1.99999 tbsp
Teaspoontsp6 tsp
Pintpt0.0625 pt
Quartqt0.03125 qt

Conversions Involving Fluid Ounce

Common Uses of the Fluid Ounce

  • Cooking — measuring liquid ingredients in recipes
  • Fuel and fluid systems — sizing tanks, reservoirs, and pipelines
  • Chemistry — measuring solutions and reagents in laboratory procedures
  • Medicine — prescribing and administering liquid medications
  • Environmental science — measuring water discharge and rainfall volume

Did You Know?

The liter was originally defined in 1795 as the volume of one kilogram of water at 4°C — creating a convenient link between mass and volume for water. The Fluid Ounce is part of the broader volume measurement story that connects everyday cooking to industrial fluid handling.