🥤 oz to mL Converter: Fluid Ounces to Milliliters

What is the oz to mL Converter?

The fluid ounce is a unit of volume from the US customary system, while the milliliter is the everyday metric unit of volume (one milliliter is exactly one cubic centimeter, and 1000 mL make one liter). Because most of the world measures liquids in milliliters and liters but the United States still uses fluid ounces, cups and pints, converting between the two is one of the most common kitchen and lab tasks there is.

The exact conversion factor is 1 US fluid ounce = 29.5735295625 milliliters. This is not an arbitrary number: the US gallon is defined as exactly 231 cubic inches, a gallon holds 128 fluid ounces, and one inch is exactly 2.54 cm. Working the arithmetic through gives 231 x 2.54 x 2.54 x 2.54 / 128 = 29.5735295625 mL per fluid ounce, an exact value with no rounding. Most people shorten it to 29.5735 or even 30 for rough mental math.

The reverse direction simply undoes the multiplication: milliliters divided by 29.5735295625 gives US fluid ounces. So 250 mL is 250 / 29.5735295625 = 8.454 fl oz, and 1 liter (1000 mL) is about 33.814 fl oz. This tool anchors on the exact factor and rounds only the final displayed result, so the two boxes always agree no matter which one you type into.

Precision matters most in two places: pharmacy and lab work, where dosing a few milliliters off can matter, and recipe scaling, where small per-unit errors multiply across many servings. For those cases keep the full factor (29.5735295625). For casual cooking, rounding to 29.57 mL, or even the friendly approximation 1 fl oz is about 30 mL, is close enough and easy to remember.

When to use it

• Following a US recipe with a metric measuring jug, converting cups and fluid ounces of milk, water or oil into milliliters.
• Reading a nutrition label or drink bottle that lists fluid ounces when your kitchen scales and jugs are marked in mL.
• Dosing liquid medicine where the instructions are in fluid ounces but your oral syringe or cup is graduated in milliliters.
• Scaling a cocktail or coffee recipe up or down, turning ounce-based bar measures into the milliliters shown on European barware.

How to use the oz to mL Converter

1. Type the number of US fluid ounces into the Fluid ounces box.
2. Read the milliliters result, which updates instantly in the Milliliters box and the large readout.
3. To convert the other way, type a value into the Milliliters box and read the fluid ounces result.
4. Use a preset button (1 to 16 fl oz) for a common amount, or Clear to start over.

Formula & method

Worked examples

US fluid ounces to milliliters chart (exact factor 29.5735295625)

Milliliters to US fluid ounces chart

Common mistakes to avoid

• Mixing up US and UK fluid ounces. A US fluid ounce is 29.5735295625 mL, but a UK (imperial) fluid ounce is only 28.4130625 mL. Recipes, medicine and drink sizes from Britain, Ireland, Australia or Canada may use the imperial ounce, so check the source before converting or your result can be about 4 percent off.
• Rounding the factor too early. Using 30 mL per ounce is fine for a quick estimate but drifts as the number grows: 16 oz at 30 becomes 480 mL instead of the correct 473.18 mL, a 7 mL gap. For anything measured, multiply by the full 29.5735295625 and round only the final answer.
• Confusing fluid ounces with weight ounces. A fluid ounce measures volume, while a plain ounce (oz) on a kitchen scale measures weight. They only match for water. For flour, sugar or oil, 1 fl oz of volume does not weigh 1 oz, so do not swap this converter for a weight conversion.
• Reversing the operation by accident. To go from ounces to milliliters you multiply; to go from milliliters to ounces you divide. Dividing when you meant to multiply gives a tiny number (8 / 29.57 = 0.27) that is an obvious sign the operation was flipped.

Glossary

US fluid ounce (fl oz)

A US customary unit of liquid volume equal to exactly 29.5735295625 mL, or one eighth of a US cup. There are 128 fluid ounces in a US gallon.

Milliliter (mL)

The metric unit of volume equal to one cubic centimeter. There are 1000 milliliters in one liter. It is the standard liquid measure in most of the world.

UK (imperial) fluid ounce

The British fluid ounce, equal to 28.4130625 mL, slightly smaller than the US one. Used in the UK and some Commonwealth countries.

Cup (US)

A US customary volume of 8 US fluid ounces, or 236.59 mL. A common recipe measure that this converter matches at the 8 fl oz preset.

Liter (L)

A metric volume of 1000 mL, roughly 33.81 US fluid ounces. Larger drink bottles and jugs are usually labeled in liters.

Conversion factor

The fixed multiplier that links two units. Here it is 29.5735295625 mL per US fluid ounce, an exact value derived from the definition of the US gallon.

Frequently asked questions