mL to Fluid Ounces Converter

About the mL to Fluid Ounces Converter

Convert millilitres to fluid ounces and fluid ounces to millilitres — type in either box and the other updates. A US fluid ounce is exactly 29.5735295625 mL (1/128 of the 231-cubic-inch US gallon) and a UK fluid ounce exactly 28.4130625 mL (1/20 of an imperial pint), so US fl oz = mL ÷ 29.5735295625 and UK fl oz = mL ÷ 28.4130625. 100 mL is 3.38 US fl oz or 3.52 UK fl oz.

Pick US or UK ounces at the top; the other one is shown under the result anyway. You also see the figure a US Nutrition Facts label would print (labels count 1 fl oz as 30 mL), the amount in US cups, and whether a container of that size meets the US airport carry-on limit of 3.4 oz (100 mL). Printable tables list bottle, can and travel sizes, millilitres from 5 to 1,000 and fluid ounces from ½ to 128.

Common uses

• Packing toiletries and drinks for a flight: is that 120 mL bottle under 3.4 oz?
• Following an American or British recipe that gives liquids in fluid ounces.
• Comparing bottle and can sizes labelled in mL and in fl oz.
• Reading a US Nutrition Facts label, which rounds 1 fl oz to 30 mL.

The formula

NIST Handbook 44, Appendix C defines the US gallon as 231 cubic inches = 3.785 411 784 L exactly, divided into 128 fluid ounces (p. C-16 and C-25), so 1 US fl oz = 29.573 529 562 5 mL. Schedule 1 of the UK Weights and Measures Act 1985 defines the imperial pint as 0.568 261 25 dm³ and the fluid ounce as 1/20 pint, so 1 UK fl oz = 28.413 062 5 mL.

• US fl oz = mL ÷ 29.5735295625 — 250 mL = 8.45 US fl oz
• mL = US fl oz × 29.5735295625 — 16 fl oz = 473.18 mL
• UK fl oz = mL ÷ 28.4130625 — 250 mL = 8.80 UK fl oz

In your head: 1 US fl oz ≈ 30 mL (1.4 % high), so 100 mL ≈ 3.4 fl oz.

US or UK fluid ounce?

The two fluid ounces differ by about 4 %: 1 US fl oz = 1.041 UK fl oz. The US one is the larger ounce, but the US pint is the smaller pint — 16 US fl oz (473.18 mL) against 20 UK fl oz (568.26 mL) — and the same goes for quarts and gallons. American labels and recipes use US ounces; British recipes and imperial measures use UK ounces.

Why US labels say 1 fl oz = 30 mL

US food labels do not use the exact figure. 21 CFR 101.9(b)(5)(viii) says that for nutrition labeling a teaspoon means 5 mL, a tablespoon 15 mL, a cup 240 mL and 1 fl oz 30 mL. So an 8 fl oz serving is printed as 240 mL although 8 US fl oz is 236.59 mL. The converter shows both.

Liquids in carry-on bags

At US airports the TSA allows liquids, aerosols and gels in carry-on bags in containers of “3.4 ounces (100 milliliters) or less per item”, packed in a quart-sized bag; larger containers go in checked baggage, and the TSA lists medicines and food for infants and children as exemptions (TSA liquids rule). 100 mL is 3.38 US fl oz and 3.4 US fl oz is 100.55 mL, so the converter treats a container of either size as within the limit. Airports in other countries set their own rules — check them before you fly.

Limitations

• A fluid ounce is a volume. Ounces of weight (28.35 g) are converted by the Ounces to Grams converter.
• The US label figure (30 mL per fl oz) is a labelling rule, not a conversion; use the exact millilitres everywhere else.
• The carry-on line checks only the container size against the TSA’s 3.4 oz / 100 mL limit; it does not cover the bag, the exemptions or other countries’ rules.
• Cups and spoons differ by country, so they have their own page: Cups to mL.

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