Fluid Ounce / Milliliter Converter

Convert fluid ounces to milliliters (and mL to fl oz) for cooking and everyday measuring

This Fluid Ounce / Milliliter Converter is built for a very specific real-world task: you have a volume in fluid ounces (fl oz) or milliliters (mL) and you need the equivalent value in the other unit quickly and accurately. This comes up constantly in recipes, drink mixing, coffee and syrup measurements, travel-size liquid limits, and product labels that use different measurement systems.

Most confusion comes from the phrase “ounce.” A fluid ounce is a unit of volume, not weight. That means you can safely convert fl oz to mL without knowing what the liquid is. You only need the ounce standard being used. In most practical situations, “fl oz” on packaging and recipes is the US fluid ounce. Some older UK recipes and certain Commonwealth references may use the UK (Imperial) fluid ounce, which is slightly smaller. That difference is big enough to matter when you are scaling recipes or mixing small batches.

Use the calculator in two steps. First, enter the amount you have. Second, choose the conversion direction. If you are converting from fl oz to mL, the result tells you how many milliliters match that volume. If you are converting from mL to fl oz, it tells you how many fluid ounces match your milliliter amount. The output includes an exact number (to two decimals) and a rounded number for quick measuring, plus a short reference line so you can sanity-check the result.

Assumptions and how to use this calculator

• This tool converts volume only (fluid ounces and milliliters). It does not convert to grams, ounces by weight, or other mass units.
• The default standard is the US fluid ounce (1 fl oz = 29.5735 mL), which matches most modern product labels and recipes.
• If you select UK (Imperial) fluid ounce, the conversion uses 1 fl oz = 28.4131 mL. Use this only when the source clearly implies Imperial measures.
• Inputs must be greater than 0. If you enter 0, a negative number, or a non-number, the calculator will show an error instead of a misleading result.
• Results are shown to two decimals for readability. For lab-grade work, you should keep more precision and confirm the measurement standard in your source.

Common questions

Is a fluid ounce the same as an ounce (oz) on a scale?

No. A fluid ounce (fl oz) is volume. An ounce (oz) on a scale is weight (mass). You can convert fl oz to mL directly because both are volume. You cannot convert fl oz to grams without knowing the density of the liquid.

Why does the calculator have US and UK (Imperial) options?

Because “fluid ounce” has two common definitions. US fl oz is about 29.57 mL and UK (Imperial) fl oz is about 28.41 mL. If your source is a UK Imperial recipe or measurement reference, selecting UK (Imperial) avoids a systematic error.

What should I choose if my recipe just says “fl oz” without specifying?

Use the default US fluid ounce unless you have a strong reason to believe it is Imperial. Most modern web recipes, product labels, and nutrition panels that use “fl oz” are using US units, even outside the US.

Why do I see a small difference compared to another converter?

Small differences usually come from using a different ounce standard (US vs Imperial) or rounding. Two converters can both be “correct” if they are using different standards or rounding at different steps.

How do I improve accuracy when measuring at home?

Confirm the measurement standard (US vs Imperial) if the source is ambiguous, then use a measuring jug or scale marked in mL for the final measurement. For small amounts, round to a sensible precision for your tool (for example, nearest 1 mL or nearest 0.1 fl oz) rather than chasing extra decimals.